Coming from road cycling and looking for sizing advice

Hi, I

'm a long time road cyclist looking to buy my first real mountain bike. I'm stuck on sizing and looking for a bit of advice.

I'm 6'3" or 191cm with a 35" inseam and ride a size L Cannondale (58cm top tube) which is suited to people 180-193cm. I'm looking at the Vitus Mithique 29 VRX and I'm right on the edge of an L (180-190cm) and an (XL 190 - 201cm). Their size chart is here

Does anyone have any advice on what size I should go for? If it were a road bike I'd probably go for the L and get a longer stem but I'm not sure the same applies to MTB's.

FWIW The reviewer on Wolfpack Adventures is 6'1 and rides an XL but it would be good to hear other people's thoughts too.