Three years ago I replaced my childhood home with a modular home. The house company and the contractors I used were highly recommended and I did quite a bit of research as well. I did find that the modular homes are usually better built. My roof structure and outer walls are sturdier than stick built because they need to withstand the strain of being transported at 65 mph. My specs guarentee that my house is built to 1/16" of being perfectly square. And we found this to be true when my brother-in-law dropped the pepper mill. Those pepper corns did not roll into a corner!
It was far cheaper than stick built. Plus, because I was replacing a house, I needed to find another place to live. Stick built was estimated at 6 months (and everyone I talked to warned me to double that time). I was "homeless" for just under two months and the reason it took that long is that we had to wait 3 weeks for the electric company to take down the wires from the old house.
My options were only limited by my budget. I could select one of their standard designs (probably 50 or 60 standard options - ranches, capes, split entries, colonials, etc.) or bring them my own plans. You can have garages attached. Every decision you can make on a stick built house you can make with a modular. I chose my cabinets, flooring, counter tops, exterior siding, etc. I chose my heating source and added central air. My windows are upgraded as well (thanks to an awesome contractor who made a special deal with the house manufacturer).
You cannot tell from the outside that my house is a modular. The only way to tell from the inside is to look at the doorways along the center wall. My house was delivered in two pieces - front and back. The doorways along the center wall are a bit thicker than a standard doorway.
When I signed off on the construction loan, the guy at the bank told me that I chose well, not only by going modular but by selecting the manufacturer and contractors I did. They had been dealing with both groups for years and had never had a complaint.