I’ve not ridden the 27.5 versions but have owned both a 26″ Five and now have a Mega TR.
Personally, I prefer the Mega TR. The back end is a lot stiffer and tracks the ground and offers more grip than the Five did. Its also a lot quieter, the Five tended to make quite a bit of racket.
The geometry is pretty similar between the two, the Mega having a slightly longer top tube, head angle being the same. I will be fitting some offset shock bushings to the mega at some point to drop a degree off the head angle, make it a little bit slacker for descending on.
Value for money, the Mega wins hands down. The quality is very good, I was quite dissapointed that my Five had multiple cracks after three years of riding – swingarm and mainframe both had cracks starting, its now hanging on the garage wall.