Farview said:
I have no experience with this amp, but 12 inch speakers almost always give you better low end. 10 inchers tend to be brittle in comparison.
That's the main deal. Bigger speakers, all else being equal, can reproduce lower freqs. Other important factors include cabinet design (open or closed back), power handling, and modern or vintage design.
In a small combo I'd probably go with the 12". But it's personal.
A closed back cabinet can help define and tighten up low end, and provides some acoustic damping of the speaker.
A low-power speaker will distort at lower power levels, becoming part of the sound of the amp at lower volumes. A high power speaker will more accurately let the tone of your amp through.
Modern speakers tend to be designed to work in two ways at different freqs. For higher freqs, the center of the cone is supposed to be able to move kind of seperately. For low freqs the cone is supposed to move as a whole. You can see a ring somewhere between the dust cap and edge of the speaker, like a ridge in the cone material. Supposed to cut down high freq damping and distortion by letting the inside part respond faster, as the voice coil doesn't have to move the whole cone. Vintage design speakers
sometimes have a cone that moves as a unit no matter the frequency, which has a different sound.
None of these are better than the other, just different. You kinda gotta listen and figger out what you like.