Dainese & Alpinestars sizing

I was going to bid on a Dainese leather jacket today that I know would fit me then just at the last minute I spotted an Alpinestars jacket I prefer that is listed as exactly the same chest size but unfortunatly I can't get out to a shop to try one on as my SV is getting delivered this afternoon and the auction ends soon for the Dainese jacket.

So my question is does anyone have experience of owning these two brands and do you find them pretty much the same or is it one of those 'I take L in that one and XXL in the other' type affairs.

Cheers

On a Dainese Website it stated:

Your chest measurement +10

So if you have a 46 chest = Dainese size 56.

Hope this helps