Number 1 impression has to be the "1. Sturmdivision 'Duuring Boven!'"
If I was far more slim, and had a horse, I'd totally do Hussar. However, I look at the cavalry in reenacting and it looks dull. My biggest pick for infantry would be some sort of grenadier (preferably French or Russian) since I'm a fucking monolith, would be silly to do a fusilier, jaeger, or voltiguer at my height and size. But, I think if I did Napoleonic reenacting, I'd go with whatever group is fairly large (not one of those groups with like five musketeers and a colonel), strives for accuracy, and is active in the continental EU (I'm not going to take a flight or boat to UK just to reenact).