There are a couple of factors to consider. First is scale length - does that make a difference to you? Zon is typically 34", while Roscoe is 35". Some people mix and match scale lengths, others (like me) don't. No right or wrong answer, but you should ponder the question.
Next is bridge string spacing and nut width. Most Zons are 17mm bridge spacing and 1-7/8 nut. Roscoe is 18.3mm bridge and 1-7/8 nut. Smith is 18mm bridge spacing and 1-3/4 nut. Some others are 19mm bridge (typical 4-string spacing). Some guys like everything to be 19mm. Others (like me) like 19mm for 4-string, 18mm for 5-string, and find 17mm a bit tight. No right or wrong answer.
Next is pickup and electronic selection. Do you like a JJ setup, soap bars, PJ, etc? Do you want active or passive (most boutiques will be active)? Do you want a certain tone profile?
People will typically recommend what they play as they like it. But there are real, measurable difference between instruments that may or may not be important to you. I've been lucky enough to own and gig a bunch of nice fretli including Fodera, Zon, Roscoe, Rob Allen, Fender, Music Man, Ibanez, and currently, a Smith. The reason I've ended up with the Smith 5-string (I still have Fodera and Rob Allen 4-strings) is that I find that the bridge spacing, nut width, scale length, and neck profile and materials work for me. I also really like the Smith pickups and electronics in a 5-string. A much more focused and "simple" tone than my Fodera, which is more open sounding.
If you're playing a lot of solo stuff then you may want a more open tone. I find that the more instruments involved, the more focused and mid-prominent tone I want. But as always, ymmv.
