Roller vs bunk is somewhat a personal preference. Neither one is better/worse for your hull since it's pretty much a standard hull (no steps). The only time that a roller is absolutely prefered is if you're loading/unloading in very shallow water on a regular basis and need to physically push it off and pull it on with no engine help. The boat will sit a little lower on the trailer with a bunk, which is good for trailering, but that's not to say that a roller is bad.
A bunk will generally support the hull better, but a good roller setup will be just fine - especially with a solidly built boat. A roller will be more money initially and more maintenance down the road.
Galv vs Alum is another personal choice. Both are durable, the alum is obviously lighter and is "prettier".
The best recommendation I can give is to buy local. If there is a problem, you want someone local working for you, as opposed to someone you've only met via a phone call. Stop by a few local trailer dealers and see what they have to offer.