I have two Wingnuts too – I’d not go back to regular rucksacks.
For the record, I’ve also used a Dakine Drafter, Camelbak Rogue, Deuter Bike 25 and 12, Karrimor something and a few others that slip my mind (obviously made an impression).
Other half has an Osprey Raptor which looks good. We had to get a replacement res though as it was punctured from new, and the hard element of it hurt my other half’s spine(!).
If I were to use something other than a Wingnut, I’d be looking new Camelbak Octane or Ultra LR, Osprey or a Deuter.