these times are crazy - anything > 10ms is slow today. You can send your grandma an e-card from NYC to LA faster than most of you can place orders.
Think of your world as being separated into three different parts:
#1 a data provider
#2 an execution engine (or front end)
#3 clearing firm
The vast majority of traders get data from, execute at and clear at the same place - a self-clearing BD like Etrade, Scottrade, etc.
The vast majority of guys with a "goldman account" just clear GSEC (note difference between GS&CO vs. GSEC). They might have a GSEC acct but they aren't invincible - they still need to go out and buy data from Activ, IQfeed, NxCore, Bloomberg, etc. but there is zero advantage to a clearing firm.
Buy data - it can be fast, medium or slow
execute - your platform can be ok, crappy or shitty (they are all terrible) (by this i mean sterling, etrade, lightspeed, scottrade, Redi, IB, etc. - all of their front ends that you stare at daily)
send orders - to your clearing firm - GSEC, Etrade, IB, scottrade, TD, etc. insert shady prop firm here....
you buy data
you feed that data into a screen
you pay to trade - fees... prop or not we all pay
you pay fees to a clearing firm that executes your trades
trading 101.
it takes 20ms for a message to pass from your eyeball to your fingertip. if i were to stand in front of you and shoot a rubber band at your eyeball it would take your body 20ms to realize that I just let go and you should probably blink.
ping & latency are relative - but should not be overlooked. guys on the west coast can hang with guys in NYC if they are pushing buttons. if you are automated and need to cancel an order that is a different story.