We're not fussy about where you post!
Nutone/Broan is the big gorilla brand. Panasonics are good, but not as widely available in store. Google is your friend.
In any brand, the big differences in price boil down to CFM, and especially noise level. With me, and a lot of people, the noise is a big issue, so I opt for maximum 1.0 sones, and 0.8 or 0.6 are even much better. You will pay a lot for the lower sones levels.
For CFM, I usually calculate a minimum 8 air changes per hour. Codes probably accept 6 or less.
eg. 10 X 12 room, 8 foot ceiling = 960 cubic feet. 8 change per hour = 8 X 960 = 7680 CF per hour; div. by 60 = 128 CFM.
( short cut: 1 cfm per sq. foot)