Fastest speed possible is not the single factor you should be looking for. Fastest speed possible for a single print design in relation to the quality of your finished product, taking into consideration what the filament type/nozzle size/printing temp/layer height/infills are is better.
Basically, there is a lot more going on than "How fast can you go?"
Many times you can't even acheive your top limits due to the small size and detail levels in a print. The printer needs longer runs to accelerate and slow down in realtion to your speed setting, if it doesn't have them, it will slow itself down to be able to make directional changes.
So, having a drag racer that can go several hundred miles an hour is fine, but if it can't make a turn without slowing down to 10 mph, then it can't drive 300 mph 100% of the time, especially if it has to make a turn every 100 feet.
Now, if you just want to print faster as a whole, a simple switch from .20 to .25 mm layer height will save you time. Changing from six perimeters to two or your infill from 90% to 15% are all simple ways to get a faster print without sacrificing quality for physical speed.
I run about 80mm/sec on a stock machine with PLA, 60mm/sec for a nice quality print. The only factor I take into consideration is QUALITY of the final print when choosing a printing speed.
When shooting for a total printing TIME, it is much easier to tweak layers and infill to get a "faster" print.
Of course, there are speed limits in terms of machine hardware/design as well. A crappy printer may not be able to print faster than 40mm/sec, yet a hyper-tuned delta printer may be able to hit 300 mm/sec under perfect conditions.
So your answer is, it depends.
