In reply to Miskawroe:
> Thanks for your response, it's helpful that you have both. Have you tried the mutant for walking and travelling much?
I've used the mutant on longish walk-ins (~1hr), it was ok, but I would have preferred the frame of the kestrel for anything longer, as it's definitely more comfortable.
> I'm leaning towards the Mutant as it is more climbing orientated and this is what I'd rather, I'm just not sure if I will loose too many functions from the Kestrel and I will start to find it annoying.
It's definitely more climbing oriented, and I'm glad I have it for that purpose. I find the lack of external features makes it feel more robust, and I don't worry about it snagging on stuff when climbing. It's a good pack and I'm pretty pleased with it, my only slight annoyance would be around the stays getting bent, and osprey being unhelpful with fixing it (thankfully someone (Toby?) here on UKC helped me out). I actually also really like the helmet holder.
That said, I have travelled pretty extensively with the kestrel both on long walks, as well as trips abroad and never had any problems. I've always taken it as carry on without issue. It's a great pack and I'm glad I have it for hiking.
If I reallyyyy had to pick one, I would probably rather climb with the kestrel than walk with the mutant, but I do a lot more climbing than walking, so I'd rather the mutant... Sorry I can't be more helpful than that!