I went with Thompson. Only other guy I considered was Kyrou. Blues were higher on Thompson than Kyrou, so I'll trust their judgement. If I based it solely on the prospect camp though(the only time I've seen either guy play), I would have Kyrou ahead of Thompson. Thompson wasn't bad at the development camp, in fact he was very good, but Kyrou really carried the play and was exceptional for most of the camp.
Based on current skill and offensive sense, Kyrou would be ahead. But, you can't teach size. After Thompson fills out and bulks up, and develops his offensive skills more, develops his already good shot even more, and learns to play a more physical game, and learns to play defence, he should be a monster power forward. At centre, he should be (or could be) a VERY valuable player, and a difference-maker. The only question is how far along his upside potential development track he will end.
In terms of upside potential, he's GOT to get the nod over Kyrou and Rattie (limited ceiling, but more ready now). Vanelli is too far away, at this point, but COULD possibly end up as a more accomplished NHLer, IF Thompson doesn't do the work to make himself a better player (e.g. busts), and the same could be said for Fitzpatrick, who COULD potentially be a Top 10-15 NHL starting goalie, but could also, easily be a bust.
At this point, I'd pick Thompson 1st, Kyrou 2nd, Rattie 3rd, then, it's up for grabs for a whole bunch of prospect, with the whole gamut of possibilities from complete NHL bust, to solid NHL regular.