We've rented Hyundai excavators in the past, a small one (don't remember the size, but it had a backfill blade on it) 210's on numerous occasions, a 250, a 290 and an OLD 320 with a hammer on it. I know hammer hoes take a lot of abuse, but this thing was a pile of junk. The smallest one seemed ok, the 210's weren't bad (we had a couple of them rented for several months at a time a few times) I liked the 250 really well, (it also had a mechanical thumb on it) I never did personally run the 290. I always thought though, that they were kind of jerky, especially the travel when you were loading or un-loading them. That said, I know 2 other people that have bought 210's, and like them.
All of these except the 320 were dash-6 machines I beleive. The only dash-7 that I have ran was a 450LC. It was a lot smoother it seemed, but on the slow side I thought.
Now, in my opinion, I would check out a Komatsu...I say this, because, we have a PC300LC-5 (about a 1991 model) with over 20,000 hours on it. It's not real pretty, but it's dependable, smooth, and still quick. It has really sold me on Komatsu machines, we bought it used in 2004, and have replaced the RPM sensor in it, and a few hoses.
Since then, we have started renting Komatsu excavators whenever we need a smaller one, or additonal machines. Right now, I have a PC200LC-8 rented, it had 185 hours on it when I picked it up. It is super fast, good on fuel, and probably the smoothest machine I have ever ran. We were told it could be bought for $160,000. I don't know about the prices in your area (this is from a dealer in Tulsa), but it's a lot more machine than a 160, for $12,000 more.
That's just my opinion though.