Road pedals will probably be lighter depending on brand and will give you a broader platform reducing the likelihood of hot sports on your foot. Also, they tend to lock you foot in better which is more important in road racing sprints (this kind o riding should never happen during your tri.)

Having said that, if you like your pedals and aren't having any problems, ignore your buddy and use what works. I personally use the SPD platform (a mtn bike platform) for ease of use between all my different bikes and they work fine.