Every waterway has it's appeal, I started with a weeks hire on the broads and bought a small boat a week later on my local river (gt.ouse), parts of the broads are very pretty and parts are flat with reeds which can wear thin fairly quickly, the Ely enf of gt.ouse is pretty devoid of charm as it's largely straight cuts through desolate fenland (just my opinion) but the tributaries from that section can be lovely.
Gt.ouse has some very pretty parts and none of the hassle of tides but plenty of locks, some love the locks as they can be very sociable but they can make getting anywhere very slow at busy times, after 12 years of them I don't miss the locks at all.
Nene is a very nice river but due to hillier ground than gt.ouse goes into flood much quicker so can be a pain.
Deben has fantastic scenery but limited places to stop as only shoreside option is at woodbridge with a short tidal window, all others are swinging buoy moorings so you need a tender, not a hire river.
Trent is pretty with manned locks, lower tidal reaches need care and planning, same with the yorkshire ouse.
I keep my boat on the southern broads and a good year for me is when I've not been near the northern rivers as I like to head out to sea and get to other places, all of which hold a different appeal.
There's no point being loyal till you've tried a few others as you could be missing out on some great things. (Don't take that as marriage guidance advice)