At least when it comes to my benefits.
I take my last final exam tomorrow, which will be the end of my first semester in college.
I had an option to go either with the MGIB or the post 9/11 GIB (I enlisted when the MGIB was in effect, got out when the post 9/11 GIB was in effect).
So after I extinguish my MGIB, I can use the post 9/11 GIB for 12 months (you can't do that the other way around).
Also, since I'm from Texas, we have the Hazlewood Act, which makes me exempt from tuition and fees, and keeping my monthly GI Bill cash to keep a roof over mine, and my soon-to-be wife's (she's finishing up her Masters degree in Speech Pathology)
I chose the MGIB because I get the most out of it. I now receive about $1400 a month for 36 months, and I get another 12 months of benefits through the post 9/11 GIB.
The post 9/11 GIB would only get me $950/mo and 36 months of school.
I still got a ways to go though...