The only advantage's with the apexi is that you can adjust boost for a set rev range, or for a certain gear(only usefull in a 2 wheel drive car).
Also, you dont need an aftermarket boost gauage, cos it has one built in, which will also tell you what the peak boost reached, which is handy to make sure you've set it up properly, and it isnt spiking.
Ive got mine set at 1.1bar up to 5k, then 1 bar after that(so it hopefully doesnt blow up)
You can either love or hate the looks of it, but TBH, if you dont like it, you can always put it in the glove box