Is my novel really Middle grade or YA?

Two weeks ago I submitted a few chapters of my children's novel to my online critique circle. Initially, my novel was meant to target the middle grade group, but some of the comments I received believed that it would be more suited for young adults.
I did a bit of research on the differences between the two and got some pretty useful information. I read my novel again and realized it was just too mature for the middle grade group. I've finally accepted that I was targeting the wrong group. Right now I'm writing on, with young adults in mind and I must say, it's great to know exactly where my novel fits.
Looks like I won't be needing those illustrations after all. I do look forward to the cover design, though.

For those of you who are confused by the two genres (like I was), here are some links that might be useful:

• Writing for children: age categories determine the guidelines for your children's book

•  Pinpointing the differences between middle grade and YA

• The differences between middle grade and young adult 

• 5 articles on the differences between middle grade and young adult 

• Am I writing YA or MG?