If you get more than ten to 20 minutes in the sun, you definitely should use a sunscreen during the day. Topical acne treatments like the ones you're using make your skin more sensitive to the sun and you don't want to burn as your acne heals.
As far as the moisturizer goes, it's helpful to compare the ingredients. I can guess that La Roche Posay is a very good product made with quality ingredients - the French truly care about their skin more than anything else (ironic since so many francais smoke and age themselves prematurely). Aveeno in my opinion is pretty blah as far as skincare goes and I wouldn't put it on my face. My hands, maybe. I'll use their body wash and shaving cream on my body. But not on my sensitive, manic face. But it may be okay for you.
But it's really up to you. Obviously, money is a factor, but clear skin is also a factor here.