Tannerite. Best target ever for indoor ranges.
But seriously it doesnt really matter for up close work. I'd go with something human shaped. Military Type E's are pretty legit. VTAC targets are really awesome too. If your goal is competition shooting circles are fine. If you plan on shooting for self or home defense use people shaped targets. Shot placement wins. Nobody's ever beenattacked by 4" dots, and you can fit a dozen 4" dots on the torso of an assailant, and only one of them will be anatomically worth a fuck if you shoot someone in it.
Every fucking gun range I've been to has the one that looks like Freddie Mercury holding an AK.
Outdoors past 50m, shoot Steel if your range allows. The instant feedback is indispensable