RE: What will a 50 cc pull?
When it comes to engines -- it's all good (except the bad ones).
The DL50 is a bargain and even if it does chuck its guts after 55 gals, you've got enough money left (saved by not buying a DA) to buy a brand new one and get another 55 gals of enjoyment.
But even if the bearings go sour -- that's not a big spend to put right -- the parts for DLs are dirt-cheap.
And the newer versions have *very* beefy mounting tabs -- the only way you'll break those is in a crash -- in which case there's no engine at any price that's immune to crash-damage.
The DLs seem to consistently turn 22 and 23-inch props at about 200-300 RPMs more than a DA and the DL mid-range seems a lot smoother.
But DA/DL -- it's entirely a personal choice and either is better than no engine at all.