Neither, Roy Halladay is the best pitcher, period.
Halladay: 12-8; 2.21 ERA; 171 IP; 149 K; 20BB; 7.45 K/BB, 8 CG; 3SHO; 1.02 WHIP
Johnson: 10-3; 1.72 ERA; 141.1 IP; 146 K; 32BB; 4.56 K/BB; 1 CG; 0SHO; 1.00 WHIP
Wainwright; 14-6; 2.23 ERA; 153.1 IP; 142 K; 39BB; 3.64 K/BB; 4 CG; 0SHO; 1.03 WHIP.
Apart from the ERA, their respective stats are more or less close, but Halladay has trow 18 more innings than Waino and 30 more than Johnson, his 8 CG are outstanding and also his amazing K/BB ratio, last night he should have trown a shutout if not for the rookie that misplay a single end his era should have been 2.16 instead.
I think if their eras are between 0.4 points appart, (1.9 v/s 2.3), if Halladay continues this trend and add between 40 and 50 more innings than Johnson (250 v/s 205), you should give the thing to him