If you only know Mesa as a high-gain amp builder, the Fillmore is much closer sonically to what Mesa built in the early years. Wonderful clean tones with an old school voicing, rich and warm with plenty of clarity, you can run this amp as a pedal platform through the clean settings on either channel. Easy to configure but incredibly versatile, you have 2 identical channels to adjust and both have the same settings. This allows you to either have 2 similar voicings at different volumes/eq, or you can have one cleaner channel and one dirtier channel.
The Fillmore really shines for Mesa in that they haven’t built an amp with this much flexibility on a very simple control platform. Throw in that you can switch from 25 to 50 watts and this amp finds a home for the house and studio or being the main amp on stage. If you have found Mesa Amps just a bit to difficult to dial in, but you want the Mesa Sound, you have found your amp in the Fillmore.