I can see there are lot more EOIs for occupation X compared to occupation Y. So is occupation X more competitive compared to Y ?

Occupation X not necessarily more competitive compared to occupation Y. Moreover, neither is the opposite necessarily true.

Imagine you're going fishing, and you have two ponds to choose from.

The first pond is huge with lots of fish, but also many people fishing there. In this scenario, think of the pond as an occupation with a lot of job openings but also high competition. You've got more chances to catch a fish, but the competition is high, so you might end up empty-handed.

The second pond is smaller with fewer fish, but there are also fewer people fishing. This is like an occupation with fewer job openings but also less competition. Your chances of catching a fish might be similar because, while there are fewer fish, you have less competition.

Neither pond is necessarily better; it all depends on your fishing skills, the kind of fish you want, and how you feel about the crowd.

For a raw look at the overall competition in terms of number of EOIs, you can look at the SkillSelect EOI backlog