Just a heads up...but bodybuilding isn't really about "health" at its core. If you want to eat more oats, then do so. As far as bodybuilding, however, it is more about what you respond better to in order to gain muscle.
Your question is a little broad. Some weight gainers like the one you mentioned are nothing like the mega-sugar drinks of the late 80's and early 90's. Back then, they had 2,000calorie shakes with nothing but a shit load of sugar.
I remember drinking one that was so sticky from the sugar your mouth would stick to the glass.
Weider had one where he claimed you could gain 14lbs in a week!!!
So I did!!
But I stopped being able to see my toes!
So yeah...your oats and whey may be "more healthy" (whatever that really means). Weight gainers are a shot gun approach....and yeah, sometimes you need a sawed off.