Interesting... what exactly do you like about the JBC, especially compared to the Hakko?
I think most (maybe all?) of these irons use bakelite handpieces which is pretty resistant to heating up, but my Pace definitely heats up the handpiece quite a bit if I use it for a long time. It's not uncomfortable but maybes slightly so if you try to grip it right near the end of the handpiece.
The thing I don't like about the Pace is that it uses STUPID plug-in "heat modules" which are just 1/8" headphone jacks with a resistor inside. On the other hand, I hated the Metal way even more, where the temp level was built into the actual tip, and if you want hotter, you gotta change tips. I absolutely HATE the fact that my hot air rework station starts from 90 degrees every time you start it up, and you need to hold the button down for a few seconds before it starts to quickly scroll the temperature. Can't understand why these guys don't put a rotary knob on the heat control - an encoder that increases temp quicker the faster you turn it. I hate pressing buttons to adjust heat.
Gee.. where to start...
The JBC heats up from cold to soldering temp in about 6 seconds, when you put the hand piece in the stand it goes into sleep mode where the temp drops to about 200degC (this is adjustable) so it drops to below the melting point of the solder on the tip which reduces oxidation while you aren't using it, when you lift the hand piece from the stand it gets to ready to solder temp in about 2 seconds, less time than it takes you to get ready to start soldering, this extends the tip life substantially.
The distance between your hand and the board you are soldering is way less, the soldering hand peice is so small and light that if feels better in your hand and you have much better control.
You can change the tip with one hand in a matter of seconds without turning off the station and the newly fitted tip reaches soldering temp in seconds, I think this feature makes having multiple irons fitted with different tips unnecessary.
It has so much thermal power it is just amazing, it heats up gnd and pwr planes in seconds so you don't need to turn the temp up you have less chance of damaging traces, pads and components while the job is just so much easier.
I'm sure I could think of more if spend more time thinking about it. It is worth every penny IMO. The hakko 936 isn't in the same league, same with the 888, don't know about the hakko FX951 though, never used one but the hand pieces look delicate and over complicated from what I have seen.