Prices for 4-layer boards and boards larger than 100x100mm have fallen significantly over the last year (driven mostly by JLCPCB), which has hugely expanded the possibilities for hobbyist electronics.
No need to compare. Go to easyeda.com. You can get 10 boards for $2 (!). I have gotten a dozen or so sets of boards and they have gotten here in less than a week. (Not affiliated, yadda yadda yadda).
Agrreeeeeed. I just did a run of 300 boards through DirtyPCBs and their quality was actually surprising. I feel like OSH Park is a bit higher, but being able to choose the soldermask and the amount of options available is crucial in some of my projects.
Maybe it's not unique, but it is a nice combination of low cost, fast turnaround, high accuracy, and with a nice interface.
Most of my 3D print experience before had been with the filament type machines, and the DirtyPCBs SLA service is a huge step up in quality, and lower hassle/cost as long as parts are fairly small like mine tend to be.
http://dirtypcbs.com/store/lasercut