Things that are infinite can still be longer or more numerous than another thing by definition. For example, two rays that extend in the same one direction infinitely can be different lengths if they start at different points.
If you limit the sets to 5 then you have
1 2 3 4 5
and
1 2 3 5
Here you have one set that is larger than the other.
The same will go for any sample you take, which means you can assume that if the set is infinite, one will still be larger than the other.
You, can't just limit it to a certain number, if I have a number sequence like adding one and then a sequence adding two, and I said that the first sequence is longer because the second one hits four first it would be illogical. They both go on forever.
1, 2, 3, 4...
2, 4...
Logically, in an infinite number sequence you can't just say this one is longer because it hits "x" number first.
But that isn't what I said.
Back in the sets of 1 2 3 4 5, you have 5 numbers.
In the set 1 2 3 5, you have 4 numbers.
Logically, if this continues forever, you will still have a set with more numbers, essentially you could think of it as infinity + 1.
You're thinking of infinity like a specific point. You can't just get there first, you can't get there. Either way both series will go one forever, so one can't have more numbers.