New Trek Domane or Specialized Roubaix & which models?

Hi all,
After a long layoff I've got back on my2009 Boardman Team Carbon road bike and I think I have the bug back to do more hours in the saddle. My road racing and TT years are behind me now (50 last year) and I'm looking for something more comfortable, I didn't even know endurance bikes existed, until I started looking last week! It sounds like the thing I need for comfy miles.
After doing some online research I'm rather confused. The Trek Domane SL6 looks great as does the Specialized Roubaix Comp. Then I started looking at the SLR 6 and wondered how much of a difference there is in between the two. I realise the frame is different and something like 200g lighter but the weight difference doesn't interest me, I can make up more than that by stopping drinking beer for a week or two. So the SL6 is £3,200 and the SLR6 is £5,400.

The big question is, what would I be getting for the extra 2K? And if I was to go for the SLR6, is there anything else I should be looking at? I don't want to spend the extra if it's not a big difference in the real world.
Any advice would be greatly welcomed!