Vet 3 snipers with a bit of devils luck can be hell on earth too, hans because he shoots so damn fast and the american one because he does it from such great distance, double vet 3 storms can cause intense pain for allied armor etc.
And a vet 3 GS KT.. say hello to mama. You might as well attack it with a rusty spoon.
Vet is gained back in just a couple games so chances are you will have to face it again.
Maybe it varies for each player, but in the long run of the games I play I reliably gain or retain nothing other than infantry vet. Support weapons will be gibbed by the type of fire they take even when used correctly. Theres a reason for why people usually have either high tank vet or high infantry vet, having to keep an eye on a frail vet 3 puma and a bunch of vet 3 volks or some vet 3 engies on one part of the map and a vet 3 qujad on the other is just too scary. <3 my puma
Theres also veterancy that increases the use of abilities like grenades or fireup/smoke that downright improves the performance of the unit and the resources of your company.