Indeed, Potions that increase one of your stats or resistance are all "temporarily" .
Me, I prefer also Allan above Barbatos, just because of that Allan Brew + I like Allan more than Barbatos, just my "personal feeling"
On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin, it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !