16 ohms would be useful if you wanted to use 2 cabs.
Specially with a 100 to 200 watt tube amp.
Alot of tube amps have limited output taps. And a pair of 16 ohm cabinets to yeild a 8 ohm load would be very useful.
Far as solid state. Then a 8 ohm 4x10 makes sense.
Likewise if another cab was needed it would yeild a 4 ohm load with 2 cabinets.
4 ohm min being very common for many amps.
As far as many people thinking a 4 ohm 4x10 would be better for " max" power.
It's not needed.
It would limit the system. Another cab could not be added. And most 4x10 are well into 10% distortion at 300 ish watts.
16 ohms also gives you the option of running 4 cabinets with one 4 ohm min head.
I'm not familiar with tech21 amps. I'm taking a guess they might have a tube amp with 8 and 4 ohm taps only.
For a healthy 8x10 rig 16 ohm cabs would be very useful