I have a KA FMT (the Tenor model) and it is a fine instrument. Mine has a pretty thick gloss coat on it that might dampen the sound some but I got that uke a while ago and I would imagine Kala has worked on this. The top is solid spruce and the back and sides are laminate.
Comparing the two ukes, since they are both Kala and probably built in the same factory I would think the construction and build quality would be pretty similar. The sound between a Solid mahogany and a spruce top ukulele will be a little different. Spruce is genarally a brighter sounding tone wood, while mahogany is generally a mellower sound.
I don't have a whole lot of experince with mahogany ukuleles so I cannot make any acctual comarisons between the sounds. I chose the spruce top when I was in the market though. I really don't think you will be dissapointed either way you go.