I suppose the question is which compromise can you live with most,
I have ridden A few 640 Advs (Phils included) be it only on easy lanes. It trumps the Tenere offroad hands down. The suspension is better (thats why mine now has 640 forks) its lighter, more responsive, more powerful and i imagine the more difficult the lanes the more the difference is apparent. But........... For me the riding postion is uncomfortable, pegs are high, bars are low. Seat is very "dirtbike" and wind protection is limited. And they require alot more maintenence than the Ten.
In my opinion the Tenere is much more comfortable. If like me you ride to the trails. The wind protection comfy seat and the incredible reliability (which is where the weight penalty comes from) ticks all the boxes.
It takes a little more muscleing around but once you are used to carrying momentum the weight can actually help.
One trick i learned is to only ever go trail riding with half a tank or less as thats 25 ish kg sloshing about up there when its full, so i inly ever put 10 - 12 litres in, the ten should easy cover 150miles on that much fuel. And its a big weight saving from high up on the bike.
I usually Ride with guys from the Trf who all have small enduro bikes. And have ridden with Phil quite a few times i think i can safely say that with practice, there arnt going too be many lanes in the UK that you cannot get either the Ten or the 640 up or down with a big grin on your face,
But your either going too be knackered or have a numb arse respectively