I would rather opt for some good whey protein, since all those mass gainers are usually full of fats and carbs, so the weight you gain is mostly fat. Therefore, it makes much more sense to use a good whey protein, and gain high quality mass. Ideally, you should choose a protein product that is made only with whey isolate, since it is the purest form of whey protein, and it has no carbs or fats whatsoever. Personally, I use the Isolation by N2BM, since it is made only with whey isolate, and has no artificial sweetners or additives, so this product is as clean as it gets. besides, it tastes pretty damn great, and the price is decent as well, so for me it is the most balanced product on the market these days.