Rollers vs bunks is mostly a personal preference as both can work well for your boat. Much of it depends on what you are used to and/or how you use the boat. You'll need to decide based on what works best for you - here are some items to consider:
-- Al vs GV: Aluminum looks nicer and is lighter. Not always, but GV is typically a little less expensive.
-- Dual vs triple: You don't "need" a triple. It all comes down to the manufacturer and the carrying capacity. Personally, I would stay away from triple because of the extra maintenance of another set of brakes/bearing/suspension/tires.
-- Speaking of brakes... highly conside Electric Over Hydraulic. Braking performance is GREATLY improved with EOH. Your truck will need a controller installed.
-- Get brakes on all axles.
-- Brands: Stay away from cheapies like Venture. Some will say they have had good luck - and I hope they continue to. But I work in the industry and have seen a VERY disproportionate rate of quality (some quite major) issues with them.
-- Rollers help when loading/unloading if you can't dunk the trailer enough.
-- Bunks tend to make loading easier and they center the boat better.
-- If you get bunks, I would highly recommend adding the plastic bunk slick option.
For "carrying capacity" - you just have to do some simple math. I'm not doing it for you!
Use your manual or look on Grady's website (and possibily Yamaha) to add up:
-- Dry weight of boat
-- Options over and above standard
-- Engine (s)
-- Full fuel
-- Full water
-- Batteries
-- Gear/ice
-- Add 10% for good measure
With the questions you're asking, I'll assume you'll be paying someone to set up the trailer (which is fine, of course). Unless you buy a completely custom trailer, they need to be adjusted to properly fit your hull. Buy the trailer from a place that can also do the fitting. Roughly speaking, it's about 2 hours of labor for someone with experience and a lift.
