[jszymborski]

I always kinda hated the cartridges and the ink that came in them from day 1.

My second pen was filled by piston and I bought some cheap Diamine samplers, and it was both simple to use and cheap.

I found converters to be often hard to use which results in messes.

[bayindirh]

You don’t fill a “converted” different from a piston one. Both operate exactly the same. Why the mess?

[jszymborski]

Piston pens have the filling system fully contained. The only place ink can come out is the nib. Converters, in my limited experience, don't always have a perfect fit or come loose during the filling process.

More deft hands probably don't have this problem. I would come out with inky hands no matter the filling system when I first started using fountain pens. Look ma', no (stained) hands!

[_pigpen__]

They’re sort of similar, but also opposite. A convertor twists up the pen pulling ink into the chamber. A piston twists down the pen creating a vacuum first. When it gets to the bottom the vacuum is exposed to the nib and the ink is rapidly sucked up. I definitely find the piston less messy.

[bayindirh]

Vacuum based filling systems are called “vacuum fillers”, like Pilot Custom 823.

A piston pen is exactly same as a converter one. For example Pelikan M605, Twsbi Eco, Lamy 2000, etc.

Vacuum pens are nice, but need more care during filling and need deeper bottles since the process is somewhat more violent.