Hi Sam,
I have a 3.5 foot iguana and several beardies. (Turtles, dogs and fish too!). I can offer you some insight on both pets. Igs are great but they grow to an enormous size when well cared for.. I rescue iguanas and some have been in horrible living situations because their owners did not anticipate their huge size. They can also be very aggressive if they are not handled or if they are sexually mature and "frustrated". The food, vitamin, lighting,housing and attention are all key ingredients for having a healthy and happy ig.
Although my iguana "Sophia" is very loving with me, she is not friendly to others in my family. In addition to giving the other family members the "stink eye", she opens her mouth
blows up her dewlap and tail whips people who try to get near her. She is a mommy's girl
. Needless to say, it is hard to find her a pet sitter. The igs each have unique personalities. I would suggest that you visit. Greeniguana.org
I'd suggest that you adopt a beardie for your first pet. They also require special care but their size is a little more manageable.
Hope this helps
Kat