A state with a large population will also be competitive for the Sens. Think about it. Every Cong. has @ the same amount of constituents, at the same time they all have 2 sens.
Look at Delaware, they have 1 congressman, and 2 senators. Thus, the odd for them are going to be better in getting a Sen. nom, than a state like VA, where they have 13 congressman, and 2 Sens.
I would not place IL., at the competitive level of CA, CO, FL, MD, NY, PA,TX or VA, but I also wouldn't put them at the level of AK, MT, or WY either.
One thing that makes some states more competitive than others is military installations. Traditionally, states with military have military children who apply in that state increasing the pool. It also has kids in town growing up going to bases for air shows, spending their youth looking up at the sky watching the Thunderbirds or Blue Angels dreaming of doing that some day.
The fact is your only concern is submitting the strongest packet you can. Even in a non-competitive state there will be candidates that do not get a nom. If you are competitive against your peers, regardless of how competitive the state is you will get that nom.
OBTW, you can always call your MOC and just ask...traditionally how many applications do you get? That will quickly tell your odds, because a slate can only have 10 on it. Hence if they have 300 historically asking for a nom, you have a 1 in 30 chance. But in the end, as I stated, it is not about how many are on the slate, it is about your stats.