What if the Bren section is supported by LT?
If you're asking about just DP vs Bren, the answer is that weapons never change with vet, only the men wielding them.
If you're asking about whether a Bren Tommy squad with a LT is better than a DP Strelky squad, the answer is hell yes, but more because of superior health and such. This doesn't change even if vet is added to both the LT and the Strelkies.