BUT....If you have ever played on the Hourglass level, you may have found that u can charge an AGT with 1 APC and when you get close enough that it cant attack, the APC has lost only about 1/2 of its total health.

If u charge an obelisk with an APC on that level, however, it will blow up about 1/2-3/4 of the way towards the tower(2 shot to take down APC), meaning it usually kills YOU 2, afterwards. So charging an obelisk would take at least 2 APCs to do in that case.

Basically, AGT is good on infantry, Obelisk is good on vehicles