I am looking to buy a Pentax MF body and fall into the price- sensitive category (I shoot primarily 35mm digital). I have access to 2 P67 lenses which can be used on both bodies (with an adapter). The P67 appears to be entirely mechanical and matrix metering is only available with the expensive P67 II. It has a bigger negative but I had film advance problems with a rental. You really don't know where the film is on this camera because it has no electronic sensors. The 645 is more electronic with multiple metering modes and electronically controlled film advance. I don't need AF. The negative is smaller than the P67. My photography is primarily outdoor nature and landscape. Is there anything else I'm missing on the list of trade-offs? Within my $500-750 budget, is one preferable over the other?