Its very silly to choose ether at this point. <_< We all know that that both devices will get revisions.
NOW, I WILL BRING UP THIS CRITICAL POINT: If you are think the ngp will be hack in three months time, you are playing Russian roulette with 5 out of the 6 chambers loaded. Sony is a big, if not the biggest, one willing to keep their device locked down at all costs. Look at the NGP's 3G feature: who is going to stop Sony from doing a forced, down-the-throat, update from anywhere? Better keep the NGP in a block of lead. Additionally, what if Sony locks down the hardware potential? Or you have go as far as authorizing with a server ever time you want to do anything?
The 3DS is a little less scary to me. The tagging feature can be prevented, (in theory), by sticking the 3DS in a static bag. I highly doubt that tagging would be enabled during game play, but you never know.
I would hold your horses for both devices. At least, until home brew actually happens and cannot be dynamically reversed.