My preference is for diaphragm regs so the USDivers would be my choice.
But.
The Oceanic balanced pistons are a straight copy of the Scubapro MK5 and the SP4 is like the Scubapro MK2....both well respected.
I dove the Omega for years when I taught in the BVI....not too sure why though, probably just to be different, it worked fine.
I do have a soft spot for the little Alpha....used them as backups on tech dives (when it was in vogue to use unbalanced regs for the necklace).
Do check the main spring of the 1st stages.....early Oceanics had a reputation for rust and I did have a spring break in two when being serviced.