Chris actually has better water affinity than hugo, with a B+ over a C in water magic. but yeah she does need to get to the mid eighties to use all four spells or use the magic stone trick, either of which is time consuming. but with 3 water rings, she gets an S in water magic, which makes her the fastest true rune caster in the game(in fact, with Jeane as support, she is can cast all true water spells faster than Sarah or anyone else with an S in water magic can cast any flowing spells). While in normal gameplay, Hugo slightly outshines Chris in magic points, but Chris has far better potential, if you are willing to work for it, and as soon as she gets past 101 mgc, she is better.
geddoe also outshines hugo, both in fire and lightning with a B+ and A respectively, compared to B's for both in Hugo's case. if it weren't for the fact that it were possible(though time sensitive) to get 3 fire magic rings, plus a wizard hat, Geddoe would always be the best candidate for the flame champion, since until you get that third fire magic ring, he will always have a higher fire magic skill. Geddoe also beats out Hugo in Lightning, although I find it easier to lightning magic rings, and Water although this is kinda silly since Geddoe can't even equip the true water rune, and there are numerous better water casters for the limited flowing runes you get.
Geddoe actually makes a strong case for strongest true rune user, given that in suikoden three, he has had his rune for substantially longer than most true users in any of the games, and lets face it, in suikoden 3, the true lightning rune is easily the most powerful in gameplay terms, although, there isn't as much destructive history with it as with some more plot important runes.