I'm looking at several boxes for different reasons. I'm stocking up on gear over the next 6 months and many are appealing right now.
TCR or Temperature Coefficient of Resistance allows you to set up TC for wire types not programmed in to the unit.
The Sig seems to be lacking in TC right now. If you don't do TC, no harm no foul.
TC Kangertech Kbox 150 is upgradable to
200W: Ni, TIi SS, NiCR. NO TCR. (upgradable)
TC Sigeli Fuchai 200: NI, Ti. NO TCR. (NOT upgradable)
TC Joytech Cuboid 150: NI, Ti, SS, Custom TCR. (upgradable)
TC Reuleaux RX200: Ni, Ti, SS, Custom TCR. (upgradable)
I own 2 - Sigelei, a 75W and a 150W and they work flawlessly, but I'm looking for something new. The 150w is powerful enough for me. I vape with a 0.2ohm coil or RDA at somewhere around 75w.
Do not buy any product expecting lifetime upgrades. B/c a box is upgradable does not mean it will come with upgrades you seek in the future.
I "think" the Reuleaux can hit 200W without PCM (pulse code modulation) where it pulses above 150w b/c it has 3 batteries. All the rest probably use PCM. This is probably neither a benefit or loss for me.