Hi ,
It depends what sort of disks you have ?
i.e. are you using hardware raid , where the requests and writes to disk will be controlled by the raid controller , which in most cases is faster than using LVM .
If you are have a VG with alot of data , then disk storage consideration is important , and whether you want LVM to control the mirroring,striping, etcc or hardware raid to do it for you LVM will obviously be slower.