A little more experience to add.....
I also think Vented dryers are more efficient, just naturally due to their design (excluding the HeatPump technology of course). A friend of mine has an Indesit Condenser Dryer ( IDCE 845 ) which is only a few months old. I've used it a few times and to be honest the results are OK.
The dryer itself is fairly quiet but seems to depend very highly on the heat so therefore gets very hot, and isnt particularly quick at drying despite getting so hot, but nevertheless it gets the job done at the end of the day. I'm yet to experiment with the cooler cycles to see how they fair, but given the time it takes to dry on its highest setting, I'd be a bit reluctant extending the time even more by using a cooler option, esspecially considering that the washer beside it spins at 1400rpm, so hardly a slow spin
I've also some recent experience with a Zanussi ZDC47100 condenser dryer, this esspecially in comparision to the Indesit works alot better in my opinion, it dosnt seem to get quite as hot, drys faster and is even quieter than the Indesit, the parts also have a nice weight about them too, nothing is really too flimsy. Though it does get quite a bit hotter than most other vented dryers I've used, maybe thats just how condensers typically are

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Ive also had two White Knight dryers, albeit compact versions but they both proved to be total workhorses

They may not boast the most up to date features but their design really is tried and tested, may not be the best of the best but they sure do last

My first was roughly 12 years or so old before the belt snapped, and the second dryer was just under two years old and was sold on as I wanted a full size dryer

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As Haxisfan menntioned above, on the first look they do seem very flimsy, the doors are very light and do seem like they would literally snap off easily, but suprisingly they seem stronger than they look, enough for simply opening and closing on a daily basis anyway
Hope this helps
Rich