ABS vs PLA 3D Printer Filament

Can someone very simply, detailed, and thoroughly explain what the main reason someone would choose either PLA/ABS over ABS/PLA?
Answer #1
abs is more durable as far as dropping, and handling. you can throw parts on the floor and not much will usually happen. PLA is a bit harder and can break easier. that being said, either works well for reprap. IF you use PLA you will want walls to be thicker, infill to perhaps be higher and more plastic overall, and lots of fan cooling to keep down creep or warping of parts from mechanical stress of nozzle moving in above layers.
As for quality of prints PLA is more accurate and allows higher resolution builds as long as your machine is capable of pushing PLA.
PLA allows higher print speed, more accurate placement of material with proper cooling (it does not shrink as much) and also thinner build heights because of less resistance from the plastic coming out the nozzle, where abs even at high temps (252C) is still sticky and has high viscosity.
So my take on what to use is if you need to make a model or small part to show and it will never be exposed to heat cyces. use PLA. If you need to fix something or use the part for something where it will have mechanical stress. make it out of ABS.
This is of course assuming these are the only plastics you use.

Answer #2
abs is more durable as far as dropping, and handling. you can throw parts on the floor and not much will usually happen. PLA is a bit harder and can break easier. that being said, either works well for reprap. IF you use PLA you will want walls to be thicker, infill to perhaps be higher and more plastic overall, and lots of fan cooling to keep down creep or warping of parts from mechanical stress of nozzle moving in above layers.
As for quality of prints PLA is more accurate and allows higher resolution builds as long as your machine is capable of pushing PLA.
PLA allows higher print speed, more accurate placement of material with proper cooling (it does not shrink as much) and also thinner build heights because of less resistance from the plastic coming out the nozzle, where abs even at high temps (252C) is still sticky and has high viscosity.
So my take on what to use is if you need to make a model or small part to show and it will never be exposed to heat cyces. use PLA. If you need to fix something or use the part for something where it will have mechanical stress. make it out of ABS.
This is of course assuming these are the only plastics you use.

awesome info, thanks brotha
Answer #3
Why PLA?
PLA (short for polylactic acid) is a plastic made of renewable starches such as corn and sugarcane.
It is biodegradable and does not emit a lot of ultra fines particles (UFCs).
It produces a barely noticeable, but quite pleasant, sugary smell when extruding.
Depending on the specifications and the color, extrusion temperature can vary between 160 and 220 �C.
Parts printed using PLA are more rigid than ABS parts (ABS is more flexible).
In general, parts printed using PLA have a slightly glossy finish.
PLA is less prone to warping during print and is much more �stickier� than ABS.
PLA starts to become malleable (heat deflection point) at around 60 �C.
PLA requires a bit more force to be extruded as it has a higher coefficient of friction than ABS.
PLA is a bit more recent in the history of FDM 3D printers and has a promising future.
Why ABS?
ABS (short for acrylonitrile butadiene styrene) is a common thermoplastic (LEGO blocks are made of ABS) that is essentially pretroleum based.
ABS is more prone to producing UFCs when compared to PLA. Good ventilation is recommended.
It produces a slight �burnt plastic� smell when extruding.
Depending on the specifications and the color, extrusion temperature can vary between 220 and 260 degrees Celsius.
Parts printed using ABS have a �bend� to them and are less brittle than PLA.
In general, parts printed using ABS have a glossier finish than PLA parts.
ABS starts to become malleable (heat deflection point) at around 100 �C (which makes it more heat resistant than PLA).
ABS has a lower coefficient of friction than PLA and requires slightly less force to be extruded than PLA.
ABS can be considered the �legacy� type of filament since it was used for 3D printing before PLA.
Taken from http://bootsindustries.com/portfolio-item/importance-of-good-filament/
A lot of other handy info there too.