The 121/101 combination sounds great to me, easy to get a range of different tones with both mics on the same cab, just by mixing them together with different ratios.
To me the 101 has a bit more midrange, which really fits well for electric distorted guitar, the 121 has the oomph and just enough top end not to sounds scratchy on guitars and reveal the shortcomings of the output transformer in the amp. Both mics have a great sound of their own, both mics sound great by themselves in front of a guitar cab, but the combo kicks ass.
So, in typical Gearslutz fashion: use both...