I work in this industry and I'm a 3D Systems reseller. The fist thing you want is a temp controlled build chamber. While the open units are able to print some pretty cool stuff you'll have greater success if you can maintain the build environment temp.

ABS and PLA have their pros and cons. So does a dual or triple extruder machine. But please be aware some multi extruder units can accidentally contact the model and cause layer separation.

Another option is to just contract out the parts you want made. That way you don't need to keep up with the changing tech.

However if you want a 18 micron job done in your own home I'll gladly sell you an 85k printer. Or you can buy my used demo unit for 65K. LOL