All the Spotmatic cameras seem to be virtually identical.. except for the last Spotmatic F/es/esii.
We're there any that were designed to be upscale/professional?
What do you consider to be objectively the "best"?
There are many subtle differences between the spotties.
The Spotmatic SP has actually two variations, because the SP model was silently updated during production, with a smoother mirror action. You can distinguish the change because the second iteration (NOT the SPII but the SP, second iteration) has a different typeface on the shutter dials (and other cosmetic differences).
The SPII has this smoother mirror action and some more updates:
- "improved shutter" according to Pentax
- film guide roller
- hot shoe
- improved metering range
However, SPII prisms tend to have faults today, while SP prisms usually are find in perfect shape.
The SPIIa (which I own) is a rare model, almost identical to the SPII but with an added sensor for a specific Honeywell flash.
The Spotmatic F might be the most desirable due to wide-open metering, however it uses a circuit similar to the one on the K1000 which means no more on-off switch, but it will depend on a lens cap to turn off the meter. I don't like this and would prefer a switch. I don't have a Spotmatic F by the way, so this is based on my experience with the K1000.
The Electro-Spotmatic must be the most beautiful of all, but it has serious reliability problems.
The ES ought to be the best but the manual selection of speeds is much more limited than the others.