TC, we changed our holding tank and hoses early this year, with mucho help from Peggie. The new tank (Rich, at Ronco) is larger than our original (mis-labeled) and we made all the innies/outies on top of the tank, so we were able to increase capacity by about 60%. We used SaniFlex hoses, and it's very easy to work with, bends nicely.
Some points about tank fittings that weren't obvious until afterwards. First, Rich/Ronco did a very good job installing what we (thought we) wanted, where. OTOH, overhead clearance was an issue, and it wasn't until after the tanks arrived that we learned aout some other Ronco options. They spin-welded 1-1/2" and 1" fittings on top, threads above the top surface of the tank. Had we known they offered the option, we would have specified threads inside the tank (flush fitting) 'cause that would have saved us about an inch of overhead space. Also, the default dip tube/elbow they provided was a 3-piece thing, about another inch too tall for our application. The option we hadn't known about is a two-piece elbow/dip tube that saved us that inch. Together, flush spin-welded fittings and the two-piece dip tube/elbow assembly, would have been niftier. It worked out OK in our case, but we were initially in a bit of panic... until we explored options.
We used four fittings; one innie (inlet from toilet), two outies (separate outlets to deck pump out fitting and to overbeard macerator), and one outie for the vent outlet. That configuration, along with the dip tube approach, should make future maintenance on any one hose or on the macerator pump slightly easier, less messy.
I used SaniFlex for the hose run from toilet to tank, but... there's a dip in that run, so it's always got standing waste in it (unless I flush a few gallons at a time, not a great alternative). PVC would have been better for that one rune... and it's what I'll use if I ever have to replace that one SaniFlex hose. I didn't this time because I've not worked with PVC before and because there are some complicated bends that I'd have had to solve.
Were it me, replacing the toilet, I think I'd be looking at whatever bowl might fit the existing mounts. If Jabso, so be it. 37045 Quiet Flush electric freshwater, in our case. Ours works fine, it's sorta quiet, at least when the motor is new, and when compared to the loud POP!!! that happens when you light off a VacuFlush at oh-dark-thirty in the AM. Otherwise, if a straight one-for-one swap isn't in the cards, Peggie's usual Marine Elegance recommendation sounds OK to me.
-Chris
