I maybe go for the EMT first too.
If it's "excellent condition" as say, the price is good, are the remote include?
Be sure everything is fine, some obsolete component inside and i'm not talking about transducer and pickup on the plate :-X
I would also say EMT... but... if you could get 140 and have a place to put it - that would be even better. The thing is the 140 is easier to repare or fix if anything goes wrong... I couldn't say the same for 240... or bx20 if you wish. All three (sorry for 140 bug) are totally different animals... maybe 240 and bx20 are more similar but still different.
If I would have money and place to put it I would get all three... but 140 is the priority
The other thing is price. I think the price should be 300-500eur lower for each one! Except if they are in mint condition... but anyway. In that regard try to lower the price. There are some people who caused the prices for the gear are inflated (like the flower pot guy) but they shouldn't be. (I've seen the 240 for 1000eur and bx20 for 600eur about half a year ago)
My advice: go and check them both (very extensively)... go home and sleep it over... then decide. When you buy one there is only the matter of time when you'll get the other