Here are my foundings I had a nokia e71, nokia 5230 and blackberry 8520.
Touch screen:
It looks awesome. You can watch movies and videos with ease and enjoy it fully. Web browsing is awesome. Typing takes a little longer because you can't feel the buttons although there is swype(a faster way to type). I've never had a unresponsive screen, in fact it responded very fast. Image browsing is also very enjoyable.
So in short I would say, touch screen you type slower but you enjoy other features like media browsing.
Qwerty:
I enjoy my qwerty keyboard phone chatting, I type very fast but you can hear the buttons on a blackberry(but not nokia qwerty) so I couldn't secretly chat but I responded quickly with a ease. Media browsing isn't so attractive but it works 100%, I would disagree with an answer above, most phones with keypads have a search function, which makes searching for a song faster! Qwerty keyboards usally takes up more power than touchscreens and qwerty keyboards are thicker
So my conclusion is touchscreens are slim and made for media browsing and gaming, their typing is functional and silent. Qwerty keyboard phones are thicker, take more power but chat with ease but make small sounds when typing. If you plan to buy a qwerty phone ask the friend if you can type on their phone just to feel it, nokia and blackberry's layout differ and the nokia's keypad is silent.
I recommend you feel for yourself, ask friends who own touch and keypad phones and try them for a few minutes. Also try different brands because some brand's touchscreens differ from others and vice versa with qwerty.
Hope this was an elaborate explanation, mail me for any questions.