My pump came with a ‘rubber ball squeezy pump thingy’, and the gauged pump was an optional extra.
I used the gauged pump for the first time with water very carefully to get a feel for the Hg reading, then used the cheapo pump from then on as it has no rustable parts.
The main benefits I noticed were
1. The hydraulic method had a much more firm response than pneumatic
2. Condensation/visibility was never an issue
3. Nice and warm for a while
4. Getting a seal was easy
5. No lube required
On the neutral/downside:
1. No way to keep the water warm unless in a bath
2. A lot of hassle
3. It didn’t seem to do much that air pumping didn’t, except perhaps slightly less edema
I’m not a frequent pumper though, as I haven’t found any benefit (maybe I should transpose those two word groups?)