Bigger (wider OR deeper OR both) will catch more goop and is better from that standpoint but you also have to LIVE there, so it can't look too huge and you have to be able to give up the cabinet space. Soooo, it's a personal thing on where you want to compromise. And really, having them the same width is going to be plenty good for just about most cooking most people do. (Looks like Paddy's is an extra deep model, which is one way to catch more crud without wasting cabinet space. Looks great--but in my kitchen, for example, it would overwhelm my narrow galley.)

It's a universal recommendation that the hood be at least 6" wider than the surface it covers. And as deep as you can manage. It has nothing to do with the fuel used to heat the food. It has to do with the fact that smoke, steam, smells, and aerosolized grease particles rise upwards and outwards. That's physics. A smaller hood can't capture all of those yucks. Stronger fans can't compensate for a lack of capture area either. It's more important to have a good capture area than a strong fan.

Check Overstock. We bought ours from there when we remodeled and I love it. It's bigger than yours but they had a ton of different options at good prices.

First please describe any limitations on the duct size, the duct length, whether an external blower can be used, and how you intend to make up the air pulled from the apartment by the blower (as opposed to gagging it with no make-up air).