He is a 20/10 upside guy with better defense... whereas Vando is more like 15/10 (and that is being generous to Vando, since Collins has produced 20/10 and Vando best season is this season with 8.5/8). Offensively Collins is a good shooter and an elite lob finisher and PnR guy.. which is one reason why Capela being healthy drops his numbers. He is not great with the ball in his hands and doesnt self create.. so spot up, PnR and lobs.
Vando is a better passer and ballhandler as well.. but the difference is not great. For shooting.. Vando starter the year hot and Collins started it cold as ice but he has a history of being much better and more frequent 3P shooter taking 3-4 attempts per game for his career (career avg .359 and career best season .409).
Vando is 2 years younger though... but since both are young I dont see that as a huge advantage. Biggest advantage for Vando is his contract. Collins' is not good.. albeit I personally think he can live up to that.
Check out this highlight reel from last year and that gives you a clear idea about the type of things he does that Vando doesnt.
View: https://www.youtube.com/watch?v=LIzcIj0Lpyk