Just did a search for Advantage vs Velocity decks and found the Scag ads about both decks. From what I see in the ads, the Velocity deck has a larger discharge opening, but otherwise very similar to each other. There may be a dimensional difference front to rear of the decks and the machine frame sizes may be different. Several years ago I did some repairs to 36" walk behind, mostly welding, that had an Advantage deck and Scag still uses Advantage decks on some machines, walk behinds and V Riders. V Riders don't sell very well in my area, not sure why though.
As for my Tiger Cub with a Velocity deck, I think that it blows out too much, but just my thoughts. Most of the time I use a collection system, but last summer I bought a blocking plate and put mulching blades on and did this all season until fall and spring cleanup. Today I changed it back to mulching and probably will leave it this way for this season. I put the standard front baffle back on and I have it in the lowest position where I also put the collection front baffle. I keep the plastic chute and tools handy in my trailer so I can side discharge should I feel the need to when on a job.