I've used both, so here's my opinion:
Calgary area, Telus is an
excellent provider. Calgary is their hub, and they built a very good network there. Even in the C-train in the tunnels, you won't loose a signal.
As for the rest of the province, both networks are seemingly identical.
The reason you have frequent delays of 10 to 20 seconds after you press "SEND" is due to traffic on the network. The more traffic, the longer it will take to process a call.
When someone calls you, it will never be symmetrical ringing. This, again, is because of the network. When someone calls you, the network needs to find where you are, and then the closest tower to you needs to send a signal to your cellular phone. This takes more time than a landline which is hardwired. Therefore, you will always have that delay in the cell phone.
As for which to go with, either is a good choice over any
GSM network. However, I must also point out that Bell plans to be bringing the
EV-DO network to Alberta this year.
EV-DO (EVolution Data Optimized) is wireless high speed data access for your phone. So, take for example you're downloading ring tones, screen savers, browsing the web, etc. Right now with the 1X network, it's about as fast as dialup internet for your computer. With
EV-DO, it'll be about as fast as high speed internet. Around 500 KB/s to 700 KB/s. Bell is the leader in Canada for wireless data connectivity, so that is something to consider.