Upgrading stock tubeless tyres - is it worth it?

The Pro Ones aren't thought of highly on this site, especially for wet weather grip. I've got them on and completed 4 rides, one of those was an early morning ride with damp roads, I didn't notice any skittishness.
Slicks are fine, the tread doesn't disperse water or provide any grip. My winter bike has a clincher tyre on that I find ridiculously good in wet weather (but its a heavy tyre and not great rolling resistance) - From Sheldon Brown....

"Bicycle tires for on-road use have no need of any sort of tread features; in fact, the best road tires are perfectly smooth, with no tread at all!

Unfortunately, most people assume that a smooth tire will be slippery, so this type of tire is difficult to sell to unsophisticated cyclists. Most tire makers cater to this by putting a very fine pattern on their tires, mainly for cosmetic and marketing reasons. If you examine a section of asphalt or concrete, you'll see that the texture of the road itself is much "knobbier" than the tread features of a good-quality road tire. Since the tire is flexible, even a slick tire deforms as it comes into contact with the pavement, acquiring the shape of the pavement texture, only while in contact with the road."

Coming off in the wet could be down to tyre compound, or it could be too much pressure in the tyre, or a combination of the two and maybe taking a corner too fast? My view is the wider and softer you can go the better...that doesn't mean too soft so its not optimal, I'm 70kgs with my winter fat, I run my 32mm winter tyres at anywhere between 55 and 75psi depending on conditions / road surface etc.

I don't think I'd notice. You'll notice other characteristics about the tyre more than the weight. Presuming your UK based, at this time of year I'd be more concerned about the grip and puncture protection of a tyre (including tubeless puncture/damage resistance). My bike with the Pro One's goes into hibernation next week, out come the slower tyres with good wet weather grip.
https://www.bicyclerollingresistance.com/ is a good place to start reading about the speed of tyres, but this is very much on a drum/lab conditions rather than real world, but still worth reading.
With regards to 150 grams, a hill is still going to be a hill, will still require x number of watts to get up it at a given speed. It may be approx. 2 or 3 seconds difference (depending on the hill), but I don't think as a rider I'd notice that weight difference. Maybe if I was comparing the power difference, it might be 215 watts with the heavier tyre and 214 watts with the lighter tyre.....(not scientific just trying to say the power difference with 150 grams is minimal). (I know its better to save weight from the tyre/rim, but 150 grams won't be hugely noticeable). If it was weight saving and also lower rolling resistance, aero on your rim etc, then its worth the change.
What would be noticeable would be coming down the other side of the hill confident in the tyre and its cornering ability. Plus not having to stop somewhere to fix a flat or a cut in the tyre.
Maybe get a good grippy / heavy tubeless tyre for the winter and move over to a faster tyre in the spring?

As always with the cycling industry nothing is ever simple.
Schwalbe, Continental and Sheldon say that on road the tread is nothing more than an aesthetic add on and offers little or no actual use. (Schwalbe and Continental being large manufacturers of slick tyres)
Compass, the people behind Graeme's link who make treaded tyres say tyres should be treaded. They also say wider tyres are faster and they describe a study conducted by Bicyling Quarterly to show this.....Jan Heine, Editor of Bicyling Quarterly, is also the founder of Compass Tyres.
https://janheine.wordpress.com/2018/01/ ... re-slower/
As someone who rides wide tyres during the winter, I'd agree that for winter riding wider lower pressure makes sense. But they are by no means faster. There are too many other considerations that I don't believe that study has taken in to account....actually its not a study, more a sales pitch.
Compass make some great tyres, super comfortable ones for long distance. But my unscientific study of one shows that the Compass Bon Jon is not as fast as my 25mm Michelin Power Competition for 99% of my rides. The Compass tyres I had were really nice and smooth, infact I'd have another set but they are just a bit too wide for my rims. I certainly wouldn't use them for racing on or even for fast training rides.

Firstly I'm a fan of Compass Tyres, they really do have a place in the market and are a great tyre.
Secondly though, it does feel like a conflict of interest, I'd even say that the main study Jan refers (Tour Magazine) is also not real world based, didn't they use a dummy in a wind tunnel?
As mentioned, I wouldn't race on them. In a race we tend to average approx. 25mph, there will be times where we are riding over 30mph (in excess of 300 watts and close to going into the red).The difference in rolling resistance and aero could be the difference to me riding at threshold or going above. The total difference may only be about 15 watts, may be more may be less. This may seem minimal and go against what Compass say. Either way I want to ensure I have the most efficient set up as possible. I'm not overly concerned about flats so durability isn't a concern.
I can't see how a 35mm tyre on a 17mm internal rim is efficient. Personally I prefer to look at what engineers who specialise in the field (and I'm not trying to be disrespectful, I just don't see how a roll down test performed in 2005 equates to real world physics involved in road racing)
When you read the methodology differences between the Cycling Quarterly tests and those performed by Hambini, it makes me side with the aerospace engineer. Hambini's finding show that a narrow tyre (23mm) has less drag than a 25mm tyre in real world scenarios.

I had the 35mm Bon Jon Pass, I will get another set as they were a really good tyre. But absolutely no way can I race on that tyre. I may be weak and old and need every advantage I can get, but for racing I'll stick to narrower tyres (not over inflated). For weekend rides once my 32mm tyres are worn out I'll get some Compass tyres as I really do like them, and to be fair most tyres made by Panracer are uber comfortable.

Also, Jan's findings were over a decade ago. Why hasn't this transitioned to the Pro Peloton (surely Sky would be looking at marginal gains)? Even at my lowly level of racing, I've never seen anyone rock up on wide tyres than 28s? Not talking about cobbled classics, but general road racing. I've used 28s Corsa G+ a lot for spring series, but wouldn't want anything wider than that.

Thread may actually have a positive impact on aerodynamics.

All conti tyres have a tread pattern.

The grippiest in the wet tyres I have ridden on all have a good tread pattern. Of course the file thread pattern may have nothing to do with that. I can't really tell as the no one makes the same tyre with and without thread for anyone to know.