The DigiSearch is I think the current model being sold. Any of the meters will work. You mainly have to be concerned about it's resolution. Most people use a meter that goes up to 180 in VDI, though some prefer older meters that went up to 540 or 550 (can't remember the exact #). The 180 scale makes targets lock on much more solid, but there are a few who like the patterns they can see in a higher scale slightly better. I find 180 to give more than enough scale compared to any machine I've used. Most are much lower than that. Even the M6/MXT, which have a great reputation for splitting hairs on pull tabs versus rings, are slightly lower in resolution than the 180 Sovereign meter, making it more capable....not to mention a Sovereign's higher number of tones and better depth.
There is also a bar graph meter out for it that some like. The older meters can be re-calibrated to a 180 scale with a resistor or two. Then there is the aftermarket internal 180 meter that is installed in the speaker hole. Guys who hip mount really like that unit. It would be much harder to see if you mount your box on the shaft, though.