1/4" jacks are nice...but the reason I prefer them whenever possible has nothing to do with audio and, instead, has to do with what happens when the output cables get yanked really hard. Enough force can bend or snap a 3.5mm plug, but 1/4" plugs are far more substantial. And accidents like that DO happen!
FYI, don't go smaller than a Mantis if you've not bought a case yet. I've seen dozens of Rackbrutes, Palettes, et al get jammed out with "sexy" modules, resulting in...well, nothing in quite a few instances because the "utility modules" were totally ignored. The smaller cases (below 2 x 84) are far better suited for what I call "mission specific" builds instead of generalized builds resulting in a full-on modular. Small cases (without some good discipline on the part of the user) also result in potential fails such as teensy controls that have to be adjusted with tweezers because your fingers DO NOT fit. They also tend to be builds in which essential modules get left out; this is particularly awful when someone opts to jump into modular without advice, buys everything, and then wonders why their "modular synthesizer" doesn't work and/or sounds like refried garbage. Basically, it's pretty simple to put together a good basic build just by skimming the forums here, or hanging out on The Site Formerly Known As Gearslutz or The Site Formerly Known As Muff Wiggler and observing the "traffic". But it's EQUALLY easy to spend thousands on a compromised pile of crap, especially when not paying attention to all of that advice. In fact, some of the best base-level info to remember can be found in Jim's sigfile above.