I have them both and and from them I choose Elmod xD I use IBU2 in my Jagdtiger and Open Panzer in my Oddball's Sherman.

IBU2 pros: easy to setup using SD card; plug and play with Heng Lond and Taigen; great sound, good if you want basic tank operation
cons: limited configurability

Open Panzer pros: great flexibility, control over everything
cons: need sound card (in my case TBS Mini) and additional ESC, not plug and play (i.e need rewiring Taigens mechanical recoil), not available anymore anywhere

I've bought OP very cheap on sale with Oddball's Sherman in mind, mainly to put many songs and have realistic movement