I think the P4 client only converts to the full-game client on PC only.
If you're downloading the full-game client right now, I don't see much reason behind keeping the P4 one. You never know with SE, though.
FFXIV: Raxion Gunsoul - Brynhildr - 50PLD 50SMN 50SCH 50DRG
WoW: Raxion - Greymane- 90 Druid
FFXI: Nion - Asura - 99 BLU, PUP, SMN, DRG, PLD 50+ DNC, NIN, MNK, THF, WHM, SAM, WAR