I have an original Arizer Solo and a Boundless Tera, and was going to stay out of the conversation because the Solo battery is unbeatable.
However, I decided to quantify that knowledge by seeing how many sessions each gave on one full charge.
I ground up sufficient quantity of herb for the series of sessions to remove that experimental variable. I also used the two units in as exactly similar a manner as possible to reduce the users 'usage pattern' variable.
I have been using the Tera as a direct replacement to the Solo and use the same solo stems in both heaters. My Solo sessions start at #5 then jump to #7, and I cache the loads.
For the experiment, I alternated the Solo (at 5&7) and the Tera (at 200 and then 220 Celsius; the Solo reaches 210). Both had been overnight on the charger.
The results were seven Solo sessions and four Tera sessions. The Tera would not heat and turned off when I attempted a 5th stem.
A Solo stem works well in the Tera, reducing the load volume. Because the glass heats up, conduction does occur as is true of the Solo also.
Personally I consider the Solo to be more efficient at extraction but since many do not toast and toss ABV like I do, the noticeable (even to me) taste and delivery of the Tera may attract.
As to portability, It is large and is heavier than the Solo, and when using Solo glass has the same breakage issue. One may need to carry a second pair of batteries if the day is long. A long day away from home is possible with a backup battery set and a Storz & Bickel cassette of dosing capsules, using the plastic mouthpiece (remove the screen and cut about 1 mm off the gasket and place a 1/2 inch Solo screen inside between the plastic and gasket).
The Arizer Solo is simpler, basic; the battery best.
The Tera is more versatile, with multiple use modes, one-degree-step temperature settings and a high-heat mode.
Using Solo glass in the Tera requires the use of one or two hi-heat silicone "O" rings (Solo mod), but no other modification.
Curiously, I can use the original magnetic cover from the glass mouthpiece (removed) with one and only one of my accumulated stems.
All of the other Solo stems would require modifying the plastic-top hole.