1)Make and model of chassis?
2)"I am confused between two AIOs, CoolerMaster ML240L v2 and Corsair H100i Platinum."
-Either is fine for stock operation. Overclocking? Forget it; that requires 280mm or greater.
-The ML240L V2 is crap. There are just better options out there for similar price, in both air and hybrid.
3)"My most concern is leaking issue...."
Rare, and most leaks are caused by the users mishandling them than actual factory 'oopsies'. The 'sheep' got whiff of a rare few cases, and spread that around like wildfire.
Also, if it bothers you that much, then go air... also rare: air cooler heatpipes can burst, though that's more a manufacturing 'oopsie' - happens right away.
Pick your poison.
4)"I dont want to go for Air Cooler because it will not deliver the result as i will be doing heavy gaming..."
Pray tell, what this result is.
5)"As i live in a Hot Country and In Summers everything just melts even with the AC on!"
Very common misconception. This primarily affects chassis and cooler ambient temps, aka the temperature baseline for all your hardware; it'll never be lower than that number.
This has next to no actual affect on load thermals.
Some air is still better than no air to your hardware, even if the temperature of the air passing over/through them is 40C.
6)At the core of it all, they're all hybrid coolers. The difference is the ratio of air to liquid.
A)Air coolers: 90% air, 10% liquid(inside the heatpipes)
Strongest assets: price to performance and they last a lifetime - save for the fans.
Weakest: they just can't compete with the performance hybrid and custom loops with really high power parts - say, 300w or more?
B)AIOs/CLCs - I call 'em hybrid coolers now: 50% air, 50% liquid
Strongest assets: superior cooling for exceptionally high power parts and with purchasing new chassis that give you next to no preinstalled fans.
Weakest: the pumps are finite; when they die, the user can't continue to use the PC, so having a backup cooler on hand is a good idea.
On top of that, their price to performance is worse than air, and they're also larger - as someone who's handled both the NH-D15S and a 360mm hybrid, I don't know where people got the idea that air coolers are 'large'...
C)Custom loop: practically the opposite of air at 10% air, 90%. Not as dependent on chassis airflow as the other 2; still welcome nonetheless.
Strongest assets: the absolute best cooling and low noise potential out of the 3. No contest.
Weakest: the cost and the maintenance. The latter is what turns most people away. Also it requires you do your homework well in advance, or you can easily screw yourself before long.
Pardon the wall.