I think people who actually have played in both surfaces will give you a more accurate approach but from what I´ve seen and what I´ve been told by players, indoor carpet is the fastest surface, grass has the handicap of balls bouncing too low but that not necesarily means the surface is faster imo.
Then what about the indoor hard courts? Are they too different from indoor carpet courts? For example if we want to grade them according to their speed what will be the result among grass, indoor hard and indoor carpet courts?
There are also different kind of carpets. So you can´t say for sure which is the fastest one.
I´ve never played on real grass. I have the opportunity to play at Gerry Weber Halle which is around the corner but spending 50 Dollars for an hour is too much. I´d like to cause I also love playing on carpet, it´s an amazing speed and the ball doesn´t bounce much high up.
The indoor hard court used for San Jose is 'medium' according to the players each year. It was kind of slow the first year I went there (2002) but I think its been a little faster since then. I think the indoor courts used at Memphis are a little bit faster, since they are permanent, but neither one of those is as fast as indoor carpet.
Best twitter posts of the epic match:
@dougrobson - Whoever is supplying Mahut with hair gel needs to ink a sponsorship deal now.
@Wimbledon - FYI, with @Wimbledon live scoring devices, please add 50 to the games in the fifth set of the Isner v Mahut match.
@HolterMedia - Nice to see that a three-day test has come to tennis here @wimbledon.