do you prefer blonds or brunettes? It really is a preference thing rather than what you need. Lee Wulff showed you can land large salmon with no reel, and landed big salmon on trout gear and small flies. The difference in playing a big early fish with either an 8 or 9 wt will probably not matter.
Thus it comes down to what you like and can handle well. Early in the year you will likely face big water and bigger flies, so if you can throw that well with an 8 wt, no problem. There is not too much difference with the 9 wt single, although it might be fun to bring a two handed rig with you since this will make some situations considerable easier.
I'm fishing the Restigouche the third week of June and will bring an 8 wt single and a 10 wt 15 foot TCR two hander for fun.