I would venture a guess and say that based on the part numbers and item descriptions on Vento's site, the bulbs are different.
Phantera GT5:
Part #:GB15766.1-2002
Front headlight bulb(12V 25W/25W)
Qty 2 @ $26.00
Triton R4/GT5:
Part #: 80002BM0T001
BULB 1, HEAD LIGHT,12V 35/35W
Qty 1 @ $7.21
The bulb on the Phantera is lower wattage and is almost $6 more per bulb.
You can order parts online from
Vento
You also may be able to get the numbers off of the bulb and find a replacement by cross reference.
Hope this helps!