I'm about to get new wheels and I'm wondering if it's worth getting the 10mm version back wheel. I find that my rear quick release sometimes loosens off a bit after rough descents and I'm wondering if the 10mm axle will offer better stiffness and strength. The bike is a Blue Pig and the new wheels are downhill ones.
Pig doesn't lack stiffness or strength IMO so I don't think it'll add anything tbh. If you're having trouble with a QR loosening the answer is a better QR, I reckon. 10mm bolt-through adds weight and can make a difference to a flexy frame but it made bugger all difference in my Mmmbop.
Get a decent QR skewer - you won't notice any difference in stiffness.
IMO the 10mm version won't make a huge difference to a HT over a standard 5mm axle. If you were on a FS, I would say yes, go for it as it does make a noticeable difference - YMMV.
If you're having issues with a QR coming loose on your current wheelset, then you should look at a different type of QR (e.g. the likes of DT's RWS QRs) that you can get tighter on standard dropouts than cam-type QRs.
To help qualify this response, I use a 10mm RWS thru-bolt QR on the rear of my FS bike and have used both 5mm and 9mm DT RWS on the front and I use a 5mm DT RWS QR on my HT.
for a few extra grams id go with the through axle, i only notice the difference when riding extra gnnarrr stylleee