The sheer warmth and, well, friendliness radiating from the Friends cast when they were on top of their form was quite something to behold. Off the top of my head, episodes like TOW All The Poker, TOW the Football, TOW the Videotape, and TOW Everyone Finds Out remain brilliant entertainment. There are many, many more. The show worked beautifully when it gave something for each Friend to do, while pulling them all round a central activity. So I think when working as an ensemble the Friends cast is better. Individually, the Mother cast are probably better actors, I suppose, but that's not the same thing. I also don't really find any of the Mother characters interesting, apart from Barney.
Writing-wise, they're just very different beasts so it's difficult to compare. Friends is more zippy one-liner oriented, Mother has those too but feels generally a bit more situational (Barney's role excepted). I prefer the Friends style of comedy, though could understand why someone might prefer the Mother style.
But yeah, overall, I never really got into HIMYM whereas still occasionally watch my Friends DVDs. In fact, I might just do that later tonight.