PVRTC is a more complex format than DXT1 (which is why it can offer better compression quality and represent a full alpha channel, for instance). This also makes it more processor intensive to encode, unfortunately. At the moment, we don’t release an on-device compressor for this reason, although we are currently making a lot of progress on optimising the offline version for quality and speed. There is some possiblity that this work will be applied and made available on device in the future.
Currently for encoding, there is the texturetool command line program provided by Apple that you mention and also our own PVRTexTool suite of applications and plug-ins (which is now available for Mac OS, incidentally). The encoders are slightly different so you may have better output from one than with the other.