I would go with a dart.
Make sure you have a large sump and an overflow setup that can handle it with ease.
Last thing you want is something blocking the overflow and overflowing the tank.
The seals will go bad after time. Not a matter of if but when. This is normal for this type of pump and I would not let it concern you at all. I always keep a seal handy, they are cheap. My dart has been in use for at least 4 years now without a cleaning, leaky seal, start up issues, or noise. Can't say that about many pumps.