Everything has its advantages, the thing is from a strictly stand up point of view Muay Thai is probably the best tool but the problem is that it leaves you vulnerable to TD's with kicks and knees. Boxing while somewhat less diverse a weapon can be very effective and can be used while maintaining a fighter base which helps him to defend and TD's. Saying BJJ is not the best style though is just silly. I don't care how good your wrestling is or your GnP if you don't have any BJJ training your going to find yourself with only 3 options, snap, tap or nap. BJJ is the must have asset in the sport for anyone. Wrestlers and strikers need to now how to defend and like it or not the defense is still BJJ. There have been more sucessful fighters who only had pure BJJ (Aoki, Maia in many of his fights, his striking is still crap.) than pure wrestlers (last one I can think of Severn?) or pure strikers (Tank Abott).
"If you get hit and it hurts hit him back you not knocked out yet."-Joe Doerksen
The Toxic Terrors (FFL)
Demetrious Johnson*Eduardo Dantas*Emanuel Newton*Will Brooks*Michael Page