Definitely slightly different boots. The Agent 130's are built for freeskiing pro level riders. Dragon 120 is perfect for your all-mountain advanced/expert.

Last: The Agent 130's are built on a performance driven 98mm last, were the Dragons use more moderate 100mm width. This 100mm last is the same last used in the Agent 110's.

Flex: Obviously the Agent 130's are slightly stiffer at a 130 flex; Dragon 120 = 120 flex.

Features: The Agent series includes a shock absorbent boot board and liner, were the Dragons have a more traditional, rigid board.

Yes the Dragon 120 will rip all mountain, but if are sold on the 98mm race inspired last and 130 flex, you may want to also check out the Race Pro 130.

I always try and go with a half size smaller at least since in a few hours the boot will be broken in and loosen up. Usually I make sure that my toes are touching the end of boot I'm going to buy. Switching to a smaller size will definitely help you out.

That is a question you should use the chat feature, but you really need to try boots on. Because you have very big feet, you should shop around at ski shops looking for older models. It is easy to find great sales on big boots that are left over for from the previous year or two. My dad wears a size 31 boot. He wears a size 13 in work/dress boots, and a 14/15 in sneakers. He loves his 2006 salomon Xwave 9s that he got in 2008 for $250 (regular price was $650). They are nice and stiff (flex index of 100 or 110). As the boots get bigger, the flex index number stays the same, but the boot is stiffer than a smaller boot of the same model. This is based on the assumption that people with big feet are larger and need a stiffer boot. My brother is 20 and he has the same size foot as my dad, but he is a lot lighter (and he doesn't ski). He tried on my dad's boots and he couldn't flex them at all, but they fit him. Do you have a narrow foot or a wide foot? my dad has a relatively narrow foot. Stiffer boots tend to be narrower than softer boots, but work can be done buy a bootfitter to make boots wider in certain spots (just not longer). Make sure that you are actually a 31.5 (half sizes are not very different from whole sizes, so if you find a 31, you should try it on. You don't want to get boots that are too big or you will be in pain. Your toes should touch the front when standing, and pull back when you bend your knees forward.

Try http://www.backcountryoutlet.com
Flex of 90 so it isn't very stiff, but might be stiffer in a big size - had size 31.
http://www.backcountryoutlet.com/outlet/TEC0041/Tecnica-Diablo-Flame-Ski-Boot-Mens.html
Had size 31.5 flex of 100, still not very stiff for a men's boot.
http://www.backcountryoutlet.com/outlet/ROS0520/Rossignol-Zenith-100-Sensor3-Ski-Boot-Mens.html