I think you're going to be VERY pleased with your purchase. I've had the HH Explorer Deluxe (bottom entry) for the last year or so, and have found it's VERY comfortable. I sleep far, far better in it than I have on the ground for sure.
Don't have any experience with the side-zip yet...but just sent mine off for a 2QZQ mod #4 this week. I'm very excited to see how this improvement will work for me. I did keep the bottom entry intact rather than have it sewed up...I like the versatility of having both options.
You are going to love it! I kept the bottom entry with my Mod 4 as well.
That mod is Awesome!