I've talked to a couple of guys, which have tried the 3-phase charging on the Robitronic Expert
The problem was that the packs didnt had enough punch, so they just used the normal linear charge.
Advantages of EXP-3P:
Minimized heat build-up
Increased cycle lifetime of your battery packs
I tend to say, that the problem is "Minimized heat build-up", because GP3300 need to be warm/hot enough, to perform well.
Robitronic have made a second-generation 3-phase charger. This actually have 4 phases, in the 4. you have the option of programme a sligth over-charge, to ensure the batts are warm enough.