ANY pencil thin barrel will deflect from heat faster than a heavier barrel will. The Proof or BSF barrels have the advantage of using the carbon fiber to stiffen the thin profile barrel down so it does not deflect with heat. The downside is the cost.
If you are planning to run big mags and blast away all day a pencil barrel will not provide the accuracy, but then again what sort of accuarcy are you requiring. Some guys use volume of shots as a replacement for precise placement of shots. It is known as spray and pray.
The MRA barrel I have been shooting has proven to shoot well and is a good value. The Proof barrels on my MH and MV shoot very well and are close to the same weight as a light profile barrel, but cost is considerably higher.
Thanks! I don't think I'll be shooting a lot in a session anyways, maybe at most 100 rounds or so and definitely not in quick succession but maybe CF helps with longevity? Do you think it's worth the extra $500?