Aircrack isn't the same as a full pentesting suite. There's a couple on Android, there's enough tools to do the same on the N900. Aircrack is just the start, shouldn't be a reason to say something is the "best" though.

Perhaps that's me. But the fact that as a phone it's somewhat lacking, the fact that it's low in regards to RAM and rootfs.

That last one can be "increased" but still... the fact that Maemo is not on any other device still persists. But there's Nemo...