Which printer should I use?

Fused Deposition Modelling heats a strand of material and extrudes it.

Stereolithography uses a light source to cure liquid resin into hardened plastic.

Selective Laser Sintering uses a high-power laser to sinter small particles of polymer powder into a solid structure.

Polyjet works by jetting drops of photopolymer onto the build platform, then curing with UV lamps to bond layers.

FDM is best for larger, bulky parts without any delicate features. Depending on material, FDM is good for parts which need high strength in the XY direction of printing. 

SLA is best for high detail parts with smooth surfaces. There are different materials which can be run, including clear, flexible, grey and castable wax resins. 

SLS is best for strong, durable parts. It doesn't require any supports to be applied, so interesting geometries can be produced without much post processing required.

Polyjet is best for high detail, smooth surface parts and parts which require multicolour, meaning they don't have to be spray painted after printing. 

As it prints in thermoplastic, heat press inserts can be used. Prints can also be paused to encapsulate nuts and other fixings to improve part performance. Some technologies also incorporate laying continuous carbon fibre inside the part for further strength. 

SLA produces high accuracy parts and can print incredibly fine details. Depending on material, layer height can go down to 25 micron to achieve incredibly smooth parts which are also watertight.

SLS parts can be easily dyed and coloured. Assembled parts can be printed. Powder that hasn't been used to print parts can be recycled for future prints (but needs mixing with fresh powder). 

Multicolour and multi-material parts can be easily produced, for example hard parts with a soft, flexible over mould component can be printed all as one piece to reduce assembly time. Parts can be printed matt or glossy.