Modelling and then rigging an "organic" figure like a human or animal is one of the very hardest things to do... the mesh has to have the right poly's in the right places and also has to have the right shaping as well... then rigging said figure (specially human) is even more work. The joint start/end points have to be placed just right and then various bend, twist, and swinging zones need to be tweaked until they function properly. Mechanical items are often much easier to do as you don't need to worry about the zone of bend influence, all that needs to be set are the joint start and end points and rotation values... I can tell you that from personal experience...

I model mostly mechanical items like aircraft and ships and such, but a ways back I decided to try organic modeling. My first attempt into organics was a dismal failure... so was my second... and my 3rd... and many attempts after those as well. All total it took me about 4 years before I finally got anything to work even remotely decent.

I did finally get a full figure done and working... but it was a year of development with almost continuous tweaks in both the mesh and rigging which included 6 months in private beta-testing for additional tweaks on both mesh and rigging in the process... and even then it's not perfect, but it's as good as I can possibly make it with the skills I have. By comparison my more complex mechanical items take about a month or two to model and rig, and about another month in private beta-tests for touch-ups and to have ERC coding added when it's needed... with simpler items taking much less time.

The reason the organic took so much longer... it's a far more complex and time-consuming task to model and rig an organic figure than it will ever be to set up a mechanical one. With organics you have many more basic joints to lay out and each joint has to be set up 4 times over... first to set the joint start/end points, then to set bend-zones and influences, twist zones and influences, and side-side zones and influences... and then in a new figure there's also setting up built-in morphs, and blank morph channels to make room for future morph expansions or end-user morph injections...

Creating conforming clothes is somewhat easier than creating a base figure in that it shares the rigs of it's parent figure so some of the work is already done for you... but it can be just as time consuming if you intend to include all the many morphs and magnets that many base figures use. It gets even more complicated once you get down to specific issues with specific figures as no two are the same under the hood, even when they share a common skeleton set-up and joint rig...