Both are weight gain powders. I'll include links to both of their serving information since you can read it yourself and decide. I thought I'd talk about impressions and things I like/dislike about them.
ProLab N Large 2 The information is about halfway down the page.
AtLarge Opticen Click on the "Supplement Facts" Link.
Cost Shipped: About $42
Serving size: 90g (about 3 scoops I think)
Servings Per Container: 23
Cost Per serving: $1.83
The taste I would rate slightly above average compared to other shakes I've tasted. The mixability was much better than that of NLarge. I was able to mix it in a shaker with no clumps, and it stays mixed better as I drink it. NLarge had a tendency to separate. Opticen did not. The serving size was also smaller than that of NLarge, which was nice because I didn't feel as bloated when I drank it. Finally, and most importantly, Opticen has a protein mix. I was told in the forums that the mixture is 50% whey, 25% casein, and 25% egg. This is a good mixture imo, and considering the fact that they released this information at all went a long way in my book. There are also quite a few more vitamins and minerals in Opticen than in NLarge. Plus, it supports a forum which has a ton of helpful information that we all take advantage of.
Cost Shipped: $45
Serving Size: 152g (4 scoops)
Servings per Container: 27
Cost per serving: $1.67
The taste is on par with other weight gain shakes I've tried. It tastes much sweeter/sugarier than Opticen. If you like sweeter shakes, you might like this taste better. The mixability was ok, but it has a bad tendency to separate after you shake it up. It is also slightly (but only slightly) harder to mix so that you don't get clumps. I end up chewing up about 1/4 of what I mix with NLarge, heh. The protein in NLarge is 100% whey, as far as I can tell. That is a big one. Mixes of protein cover more bases than just one type. Also, NLarge has quite a bit more sugar in it, so if you are on a limited carb diet, it would be hard to drink these. All in all, I think Nlarge is a good weight gain shake for the $$ and although it has more sugar in it, it doesn't go overboard. The caloric edge does go to NLarge, being at 600. Opticen is only around 320 per serving. One other point about NLarge, is if you're a fisherman, when empty, the bucket makes a nice bait bucket.
If I had to pick one, I would go with Opticen mainly because of the fact that the protein is a mix, rather than straight whey. It also comes from a site where I get alot of info and can talk with other people who are in the same boat I am. Both are quality products with a comparable amount of protein. And are close to equal in terms of what they deliver for the $$, but I give the edge to Opticen for the protein mix, it's vitamin contenct, and the forums.