Every P3 I've heard sounds bright (although maybe it's the systems?). generally the MMFs are a little less $$ and more of a turn-key solution, like someone else mentioned. The rega arms are great, bu tI don't know about the rest of the table. But then again the project arms aren't as well respected as the regas and the MMFs aren't very upgradable.
I don't buy the "take the arm with you to another table" upgrade with the Regas. Sure if you do that, you are in essence left trying to sell an armless P2 or P3 on the market, and who wants to buy that table? Not many people as everyone wants the Rega arm! So in reality, what you should do with a REga is use it for a while, upgrade the cart, then buy an upgraded table, move the arm and cart to the new table and use it for a while. Then buy a better arm downt he road then sell the Rega on the used market as a complete TT+arm package. that would be better than trying to sell an armless Rega IMO. Whereas with a Music Hall, you're more or less stuck with a forklift upgrade (unless you're taking the cart with you).
The music hall can be tweaked a little. I believe LP gear sells an upgraded stylus and mat for the MMF2.1 and the MMF5 or MMF7 can use a different cart. You could also use a Michell record clamp (I do) {under $50} or defeat the suspension. I defeated my MMF2.1's suspenstion with 3 Dayton Audio cones from Parts Express (I couldn't afford the Mapleshade ones at the time, plus the mapleshade dealer hasn't talked with me in a while {What's up with that Tom??!?). I placed the three cones on the flat underside of the plinth thereby defeating the suspension in the stock feet. I place two in back, just under the motor and tone arm, and another one in right/front/middle to balance out the player. It works great I get a much wider/deeper soundstage that I did before. The effect is not subtle to me, but it is to my wife.
To summarize, for me it came down to the fact all of my auditions for the Regas sounded bright and the music halls did not. Personally I wanted the Rega to win as the project arm is a POS, but *meah*.
Aaron