I am a registered user of VoxATC version 6 but haven't used it for some time because of Ai issues.

I would like to try version 7.4 but am currently using UT Live for Ai within P3Dv4, Tegwyn advised my to not use 7.4 until the UT Bridge is updated which might take many months.  I am willing to uninstall UT Live so I can try VoxATC version 7.4 as I mainly fly in the UK and Europe, nearly all the other ATC programs are too US procedure based for my liking.

Will VoxATC work well with the P3Dv4 default Ai or is there another Ai Software I could load that works well with the current version of VoxATC ?

I am using MyTraffic6.0a with VoxATC and very happy with it. The future of MyTraffic is unclear, but there's a few posts on how to make it work with P3Dv4 by removing incompatible models.

My Traffic 6a seems to work OK for me too.

I use UTL with P3D4 and also have VOXATC 7.41. In order to test it, you do not need to uninstall anything. VOXATC ignores UTL planes and vice versa. It is not accurate and I would not like to have it indefinetly but for testing purposes it is quite alright.

What's interesting is that one can mix and match AI traffic from UTL, VOXATC (by installing MyT6 or AIG models and flight plans) and even live traffic such as PSXseeconTraffic, since each have their own activity levels for both commercial and GA aircraft.

Of course this can get awfully confusing and collisions on the ground can occur, as well as go arounds and disappearing planes. 

To my knowledge AI aircraft from VOXATC, UTL and PSXseeconTraffic all follow SIDs and Stars, unlike the default AI.

Thanks guys for your comments.

I think I'll try V7.4 with UTL still installed and see what happens, if there are problems I might try My Traffic 6.0a.