In terms of reliability, the SL 35 is the simplest and the least prone to problems.
However, many have problematic shutters or are simply beaten up for some reason.
The SL 35 M/ME is an evolution of the Voigtlander Icarex 35. The electronics on this camera are unreliable.
The SL 35 E also suffers from unreliable electronics. This is my favorite model.
The SL 2000F has a reputation for electronic failure.
The 3003 has a better reputation. I have a 3001, which is a simplified version of the 3003. It has some issue with the motor advance, which I need to sort out.