I used a mag float for years and just switched to the Tunze within the last 6 months. A few comments...
1. If you're used to the Mag Float, you'll definitely "drop" the Tunze a few times before you break your habit of disconnecting before you have your hand on it. As previously mentioned, the Tunze doesn't float. If you're like me, you'll get over that pretty quick in exchange for the super job it does on the glass!
2. True that the Tunze doesn't do corners, but at least that way I don't mess up and slice my corner seal like I'd do on occasion with the flat scraper attachment on my MagFloat.
3. I never scratched my glass with my Mag Float because I stayed away from the sand and did that area with a "scraper on a stick." With the Tunze design, I cleaned right down along the sand line... and within a couple months managed to put a scratch in my glass! If you go with the Tunze, don't let your guard down thinking it's impossible to pick up sand!
4. Get spare scrapers. If you use the plastic scraper (without the blade insert) on little patches of coraline, it'll nick the plastic scraper enough that it doesn't scrape as well as new... it'll leave little trails where it misses. I didn't expect the plastic scraper to hold up with coraline, but was surprised how little it took to lose the "like new" edge of the thing.
Overall, I'd buy the Tunze again in a heartbeat. (Sorry... no experience with the Flipper.)