Depends purely on the usage. Touchscreen is good for some and keypad for some. I use both of them. For a lot of typing, emailing etc, I use my E71 with Qwerty. For videos, photos, fancy stuff it is the touch screen phone. While touch screen looks and feels great and tempting, its not for high productivity.
Just compare writing a hub on an ipad and regular desktop/laptop. While you can sure write hubs with using an ipad, you just cant be as fast and productive as you can be with a physical keyboard.
Even in touch screens, you should always prefer to go for a phone with capacitive screens. Resistive screens are just pain and wont be as responsive.
To get best of both worlds, try a phone with both of them. There are quite a few with both Capacitive touch and keypad combination, but they could be little heavy. I initially thought of moving to Motorola charm as it was small and offered both, but the buttons are not really that good.