I agree with a 7,500 GVWR trailer as well. There are some really nice all aluminum ones on the market now, such as EZ Hauler and Mission trailers. Once you hit the 8k GVWR mark, some states kick it into a higher registration class, and it looks like NY charges by the 500 pounds for registration.
Electric brakes are fine for a car trailer. If they have the option, self-adjusting brakes are really nice, but also easy to add later. IMO aluminum wheels are a must, because they are less likely to seize in place if you drive on salted winter roads.
The other option I'd look at is tie-down locations. These are basically customer-spec'd, and some dealers do better jobs than others when they spec their in-stock trailers. Make sure there are enough tie-down for the style straps you want to use, and that you can reach them without crawling under the car. I really like 2-point wheel straps, because they still allow the suspension to work. Tying to the chassis can cause extra shock on the straps when the suspension compresses on bumps then rebounds. This shock can tear the hooks out of unibody cars. If you watch most flat-bed tow trucks these days, they've mostly switch to wheels straps for this reason unless they're hauling a pickup.
Lastly, make sure the trailer has the driver-side "escape door" option. Some brands even offer this door large enough to go all the way to the floor of the trailer, which will make it far safer for egress.