Hi there, i've seen both these subs and was going to buy the 3090. That sub is a beast in size, however the 3080 is a 10" and seems smaller. The 3090 will dig deeper, but it is smaller. If you can get your hands on a 3080 then that'll be a far better choice.
I wouldn't judge a sub by the size of the driver, some smaller subs (e.g Rel Quake) can make just as much noise as some large bulky Yamaha sub!
The 30** series where based on the old Mordaunt Short subs (MSW-20)
As for the Gale Storm 10............. AVOID THAT!! It is an awful sub, and you get what you pay for. If you wanna stick with richersounds then i recommend you get the Mordaunt Short ms308 at £150 or £130 on the net!
Thats all said for a budget sub, but if you can stretch to £215 you could get a ,Mordaunt Short MS309

from PeterTysons, with delivery and interconnect!