It's a very difficult choice. One in which i'm not even clearly sure on a clear defined answer. Instead, i'll just break it down as I see it.
Staal is a potential franchise forward, which are rare. Fleury is a potential franchise goaltender, which is even more rare. Therefore the slight edge goes to Fleury in that regard. Every team needs at least 6 very talented forwards. Each team only needs one very talented goaltender.The positional edge is far too great to ignore.
However, goaltenders that are franchise goaltenders aren't always selected in the Top 5 of the NHL draft. As a matter of fact, it hasn't hardly happened at all. Most goaltenders development comes a great deal after they are drafted, and it makes it even more of a question mark to take a goaltender early. Edge goes to the forward, Staal, in this scenario. The question of development and adaptation. Staal would be the safer pick to pan out given our current knowledge of these players.
Upside. Staal is a fantastic offensive prospect, but you have to think that his ceiling in this league is somewhere around 80 points a year. 80 real points, not, "______ could one day score 80 points!" points, the real deal. It may look like a low-ball estimate to some, but it's more realistic than a lot of the prognosticators out there are willing to admit about their own prospects. When you look at it in that light, it's possible that Staal could swing a few games in favor of his team. However, Fleury could possibly develop into a franchise goaltender to the likes we haven't seen since Patrick Roy and depending on your inclination, Martin Broduer. These players usually account for 10-15 stolen games a year, considering the circumstances. Therefore, the upside on Fluery is far greater in terms of the win-loss column, which is the only one that really makes a differance. Edge to Fleury in this regard.
Influence and leadership. These are things that are more likely to come from an Eric Staal than a Marc-Andre Fleury. Fleury is still very much immature and childlike, not ill-natured mind you, but childlike all the same. Staal brings a presence to the ice of reserved respectfulness that is shades of Francis. That's probably where a lot of the comparisons came from. Staal has the demeanor of Francis and the skill-set of a Modano type player. While Fleury could be an immense help to a defense, I don't see players being able to relate to Fleury in a leadership sense the way they can relate to Staal. It's more difficult for a goaltender to set an example anyways, if you ask me. Staal stands a chance to be a great leader, on and off the ice, for years to come. Staal takes the edge here.
It's a tough call that goes up to personal preference. I'd be honestly glad to have either in my organization, but simply because Staal plays for Carolina my natural instinct is to lean towards him.