I;ve heard all three.
The Rega P10 is ideal for a plug and play, very musical. Downside - no easy VTA adjustments. Its a great option for someone who wants great sound, but doesn't like to fiddle with TT's.
Sota gives you're more options with arms and cartridges. Just buy the best arm you can within your budget. Sota can confirm fit - usually anything from 9-10" will fit.
Both the Rega and Sota are far better than the Project in my view - both sound quality and quality of construction.