Pentax Fuji Comparison

Following on from the other day, a nice Moon presented itself as a test subject. The image shows the Pentax shot on the left and the Fuji one on the right. The upper pairing shows the relative image scale produced by the 450mm equivalent fl on the left and the 720mm fl on the right. The lower pairing has the 450mm image scaled up to the same size as the 720mm one.
What do you think? Which looks sharpest, with most detail recorded?
The Pentax sensor is an APS C 16.28mp one and the Fuji is a tiny compact 10mp sensor. Is it worth me spending yet more money on a longer telephoto lens for the Pentax? It would yield a bigger image on the sensor and consequently a lot more detail. Then again, a T mount to put the camera on my scope would be much cheaper and give me way better shots!