Powerline is slower than you think. Lots of other factors affect speed. Of course, it's not bad if you need internet somewhere in the house that you Wi-Fi doesn't cover.
Wi-Fi is decent, depends on your router and your house's walls. My Netgear 802.11g router is fast enough, but my sister's G4 Titanium Powerbook can't even get a signal out in the kitchen (which is about 50-60 feet from my room where the router is).
As for ethernet, all you need is to buy a modem and router and the service should be the same. Of course, it means more money and less freedom than Wi-Fi offers, but it's a hardpoint internet connection so it should be fine.
Speaking of that...I should do that out by the kitchen so when I get my Xbox 360 I can get Wi-Fi.
Some of the MIMO ones look good. I would probably aim for the Netgear, Linksys, D-Link or U.S. Robotics ones. They're widely known and have great products.
Up to you. I use Netgear, my dad uses D-Link at his office and I can say that both are very good companies. I've never tried U.S. Robotics, but I've heard good things about them.