What's better - VBSEO + VB 3.8 or VBSEO + 4+

I installed vbSEO on one of my existing forum, which was on 4+ and am happy with the results.

I have plans to start a new forum, and I have one free VB 3.8 license. I'm not sure if I should upgrade to 4+ and then install vbSEO or is 3.8 good enough ?

Can someone point out pros and cons ?

Thanks in advance.

There is no exact answer for a question like this. However i would go with vBulletin 3 + vBSEO

Since I'm on a budget constraint, I was planning to first work on 3.8 and once the forum picks up I'll upgrade to VB 4+.

I hope it won't be much of a problem right ?

It shouldn't be

You can always upgrade from 3 to 4, but it's basically impossible to go from 4 to 3.