The single-piece aluminum bat space is replete with options. We like bats like Easton's Beast series as well as DeMarini's one. Don't forget either about Slugger's 619 Solo or their 518 Omaha.
In terms of a real comparable bat (by way of construction), the 619 Solo is the most alike. It has a single-piece aluminum structure with an extended composite end cap and, like the 2019 Velo, comes in several sizing and league options.
Some would argue the Velo is a lot like the
Marucci CAT 8. They both use variable wall thickness, but it's hard to say these bats are too similar in terms of feel and barrel size. Where, we think, the CAT 8 shines.