I own the Nokia 3390 before w/ Fido, but now uses the SCH-T300 w/ Telus... 3390 is essential the same as the 3360...
The main reason I switched was becuz Fido's service sucks @ss...
But I like the T300 better than the Nokia becuz you dont have to keypad lock the phone everytime u put it in your pocket (it got annoying after a while), and the battery on the T300 lasts really really long (for my normal use, I only need to re-charge the T300 every 4-5 days, while Nokia is every other day)... The screen is also much better than Nokia's...
Also one thing about the nokia, the antenna is internal and on the back of the phone (above the battery)... if u put the phone face up on a table top, the antenna is between the table top and the phone... I find u have to stand the phone up to get the best reception (again, this may just be the crappy Fido network)...
the 3360 is a fun phone to have, cuz u can download ringtones and have wallpapers... but if you dont care about those, the T300 would be a better choice... It feels more solid than the 3390, which feels like a toy...
If you dont count the antenna on the T300, it is the same size as the 3360... T300 is a little thinner as well...