Rexxer units are probably very good. Given the prices, I doubt anyone but professionals are going to buy them:
https://www.rexxer.eu/e_produkte.cfm
Heck, they want 98 euros for the Fiat lead I can buy all day long on Flea Bay for 5-10 quid... Chortle.
London Electronic (website: lonelec.co.uk/lonelec.com) only rushed me 25 quid for a Fiat lead and a UK-built and tested ODBCII USB reader guaranteed to have the correct serial FTDI chip in it (as opposed to the Chinese clone/knock-off chip you might randomly get in a 5 quid no-name Chinese item).
That said; for anything other than checking a map or maybe twiddling/resetting some minor settings, you're going to want a pro with the right gear; it makes no sense to try to flash maps and test-ride them against your butt-dyno (which are notoriously easily fooled); you really need instrumentation (at least wide-band lambda) and a rolling road.
Because it's tough to find a private driveway long enough to let you see what AFRs you're getting under load at the top of 4th. Or how new PWM parameters work out for closed-loop boost control.
It's also hard to over-emphasize how much more efficient logging makes tweaking the map - as opposed to trying to do it in real-time.