In reply to Glen:
I've got both a Rab VT and a RAB Photon and I'd Struggle to compare them to be honest there both such Differnt Garments
The Proton is as you say
>Primaloft jacket with pertex quantum outer, and find it very
> warm for it's weight and nicely breathable,
Where as the VT is obvoiusly Pertex and micro pile and is no where near as warm.
I use my VT as a base layer in winter and it is execelent as that, with a second softshell over the top when it is no longer warm enough on its own. if you want to use it like that can't recomend it enough but I doubt if would be warm enough or the hood good enough as a stand alone piece. A buffalo or Montane would be a closer to the warmth of a primoloft jacket I'd guess
How are you wanting to use it?