Well the speed depends.
if you have a good wifi strength then your max sustainable speed will be your internet's speed, as it internet speed is slower than the wifi or Ethernet connection. my dad's computer is in such a position that it receives less wifi signal, a speed test shows up the results just fine (8mbps) but when browsing the difference is noticeable as it takes longer time for lookup.
so simple answer would be.. if you have good wifi signal strength (2-3 bars on 5) then you will get almost same speed as ethernet.
10/100/1000 mbits doesn't matter when it comes to Indian internet , only now we are seeing speeds up to 50 mbps for that even 100 mbit port will do.
also worth noting is that; even if your motherboard has gigabit ethernet , if your router is 10/100 then motherboard switches the speed to 10/100. so note when buying Router and modems , check if they support gigabit ethernet. also gigabit ethernet would be useful only when you are transferring large amount of data over the local network.