Always go for a vented dryer if you possibly can, I agree that they are faster and quieter, plus of course there are fewer parts that could potentially go wrong later.
Previously I had a Zanussi condenser dryer, replaced that with a Bosch about a year ago and the difference is like night and day. The Bosch is noticeably quicker, by as much as 20 minutes per load, and always finishes before the next load is ready to come out of the washer. The airflow path in the Bosch looks less convoluted, and the heat exchanger itself seems far more substantial, so I assume that's why.
As for noise, it sounds similar to the equivalent vented model, except there's also a fairly audible "whoosh" from the flow of air used to cool the heat exchanger. That's just the nature of condenser dryers, and is a tradeoff you have to make for the convenience. The only alternative is to drill a hole in the wall and install a vented dryer instead.
With regard to heating the room up, remember that if the dryer isn't exhausting the heat outdoors, it has to go elsewhere instead. Whether or not this makes things uncomfortable depends on where the dryer is installed and how well the room is ventilated. Mine is in a large open-plan laundry room and kitchen, so the heat dissipates rather than building up, therefore it hasn't been an issue for me. I would NOT want to put a condenser dryer in a closed room or confined space, however.