Advantages, no laces to get caught on anything, yet still fit tight so they support and they won't come off.
What features depends on what you want from the boot. You already said you didn't want a racey style boot, but do you want toe sliders, or not? Do you want waterproof or vents? Want high or low? Pants/leathers inside the boot or always outside?
There are some pretty decent m/c boots out there in the budget class. I've got a pair of Joe Rocket Rhino boots (this one is no longer in production, but looks like a cross between the current Revolution and Reactor boots), that have held up for 4+ years of relative neglect. They were advertised as waterproof, but they didn't prove to be in heavy rain, or if you had to walk thru standing water. Other than that, a very comfortable boot that you could wear with street clothes and walk around in all day. In fact, until I get my new boots better broken in, I still wear them if I'm going somewhere where I'll be on me feet for a while (like work or picket duty).
A couple months ago, I splurged and bought a pair of Sidi On-Roads. These boots have been around for years and get rave reviews from folks who do lots of riding in all weather conditions... kinda like the Aerostich of the boot world. The toe box has been a little slow to break in, but hopefully that's a sign they'll be as long lasting as everyone says. They ARE waterproof, and the do breathe like they say they do. They were not too hot on my feet on my 4-day summer trip, and they kept water out even when I waded in lakes and rivers to test them out.
For a budget boot, I'd also take a good look at the SetUp brand which is marketed by the same folks as Sidi and is rumored to be Sidi quality with a budget label.