happens quite a bit with comparisons. Believe a class 4 16gb microSD card goes for a little over $100 at the moment. Hopefully it'll come down by Christmas.
Will you get the full speed out of a class 6 on an 8330? I know if the phone only spins at a 4, you are just wasting your money since you wont be able to use the 6 to it's full potential
They have another brand for $50 but I never heard of it so I wouldn't trust it.
the other brand appears to be A-data. not a big name like kingston or sandisk; but i use an 8gb class6 in my nintendo ds and have never had any problems.
The class 6 A-Data at newegg is the best deal out there. It was bettter last week at $49.99 w/ free shipping but even at $56 shipped it is very good. A-Data isn't a household name but are very reliable.
As far as the class discussion:
No the phone itself is not going to benefit from a faster card but where it is going to make a difference is writing to it. Pop it out of your phone and stick in the card reader in your computer and you will thank yourself when you are transferring 16GB's of music/video/photos.
