If you are considering a smaller jet, then the LJ60 is the lowest step-down from what your passengers are usde to. It has a nice and roomy cabin, an APU (only generating electricity though) and good performance. But: it loves long runways!
The LJ45 is a nice machine as well and very modern in terms of systems, avionics etc. and it does have an APU (not the LJ40!) as well. Runway performance is good and it's certified for steep approaches. Fuel consumption is low.
The LJ31A might offer the best 'bang for the buck'. Excellent performance, low fuel flow and adequate cabin for shorter hops, but system-wise older, no APU and much shorter range.
The XLS is nice as well, but this is a philosophical discussion. Somebody looking for a LJ will never consider a Citation and vice versa.