I've had an LMII and 2 F1's (swapped one and regretted it, so bought another)
IMHO the F1 had so much more low frequency punch than the LM. I play in a band with guitard and keyboarder, so I need something to get my message across, despite their best efforts - the F1 just does it for me.
On its own, it sounds very clean, but in a band mix, it really fills those lower frequencies.
I put it through a Barefaced S12T, and it's the only amp to make me realise why I own a Barefaced :-)