Have you tested the new porbes? Satori-Horigu combat probe.
Its scan strength is the highest - well RSS is the highest if you need to go to the 0.25 AU range, but with good skills, ship and skill you will get pretty much everything scanned from the 0.5 AU range.
Reasons to use combat probes:
Besides being to able to scan signatures they can find ships and structures
Thay move faster thus you will spent less time for probing
Reasons not to use combat probes:
Hunting someone and try not to look like a threat
Useing a ship that cannot fit expanded probe launcher
If you cannot scan the sig from 0.5 AU
Here is the some comparison of the different scanner probes:
I find it interesting the RSS probes still cost almost a double compared to Satori-Horigus
Vasama