I'm a senior level nursing student at WMU so I thought I'd try to compare Western to what I know about WMU for you.
I cant tell you certainly how competitive the program is for either program. Competition in regards to acceptance into Western varies between semesters. I'd heard there have been semesters that could only accept 4.0 students because there were so many people who applied with that caliber of a GPA. But, this usually isnt the case. I got accepted the first time I tried with a 3.2. What they want are people who pass all of their prerequisite science courses with a B or better without having to retake any. You can continue to apply, and they take applications every semester, and having kept those requirements there will be a place for you. When I applied, there were no essays, references, or anything like that to turn in. Someone in the program at State would have better information in how competitive or involved their application process is. I could only venture to guess that MSU would have a higher ratio of applicants and may be more competitive in that respect
I do know that you'll have smaller class sizes in your prerequisites at WMU and the professors at Western will probably be more available to you than the ones at MSU. MSU will have huge lecture halls with classes probably taught by grad assistants whereas at Western I hardly had any class sizes over 70 people. Professors gave us their phone numbers, all had plenty available time for meeting in office hours, which was helpful to me personally but of course everyone learns differently.
Also, the professors I've had in the nursing program just want us to be successful, and have been really receptive of questions, available, and the last thing they want us to do is fail. Not to say that MSU's program might be cut-throat, I just know that is what the culture is once youre in WMU's program.
Hope that was helpful! In short my advise is to pick the program that is right for you and you'll be successful