AM IS NOT the most accurate in the US. Do not take this advice. The most accurate would be ATA, CAP, or MTK. in the US
The AM is probably the least accurate other than the FX, and is made for bigger troopers. So if you're an average or smaller trooper, I'd say go with AP, MTK, CAP, or ATA.
The AM is a fanmade sculpt and has an innaccurate chest plate not suitable for EIB use. It will need to be replaced as its too sharp and too huge.