What are the time differences between 6, 7, 9, 10 pool?
Which is suitable for larger/smaller maps?
If you're referring to Zergling timings, the standards are:
The "7 pool" and "9 pool" you're referring to would probably be variations of the above, changing the balance between "more economy" and "faster rush".
I do a pretty sick 8 pool. If played perfectly I can get "eggs cooking" at 2:11, which then hatch 25 seconds later (as of current version) and from there take X time to travel to base, either entrance or by main (CC/nexus/hatch) building.
Trick is this, build two drones so that you hit 8/10 supply. When you have 230 or 235 minerals build a spawning pool. Why not 200? Because those extra two carries that your drone makes actually helps get you rolling faster. When the pool goes down you will have 50 mins for the next drone immediately available and you will build this drone roughly 4-5 seconds sooner than if you had plopped your pool down with only 200 minerals.
So now you're back at 8/10. Build two more drones (10/10). Build an overlord. If timed perfectly with that extra mineral carry your ovie and the pool will finish at the exact same time, and there's no reason not to do this since you need both to function here.
You will also have about 165 minerals at 2:10 using this method and you need pool, ovie and money to get your lings. Great, all set. This "8 pool" still functions like a 9 or 10 pool in that it is reasonably recoverable economically if your opponent counters right. It also enables backup.
After the first 3 eggs/6 lings are out you should already have another half way hatched, and money for the next and the next. Build a queen at 15/18 so that you will have 17/18, then finish off with another pair of lings and make sure to hotkey your hatch to build another ovie as that larvae will become available at roughly the same time your first 6 lings are hitting your opponent's base.
6 and 7 pools are relatively the same time.
9 pool, just don't ..., you get no advantage from it.
10 pool hits the latest, it is less all in than the others and may make your opponent overact which will give you realy map control and pay for the cost of delaying your expo.
Maps: any small maps advantage rushes. Larger maps makes then less effective as it takes longer for the lings to get to your opponent and gives him more time to wall off and prepare himself.