I have flown the Falcon 50, 50EX and the 900EX, however I never flown a 125.
So, I'll ask you one question. Do you know of any mid-size (that's what I consider a Falcon 50 and a 125-800) jet that on most days, even hot ones, that you can fill the seats, the baggage compartment and the fuel tanks, then still be under MGTOW. In the 50EX you can. (Although I'll admit the nine passengers in the cabin for around seven hours or so would not a lot of fun for them.)
The key to the Falcon 50EX is versatility. Yes it costs more to operate, and a higher purchase cost, but remember, you get what you pay for. The last Falcon 50EX I operated just sold for under $13,000,000.00, it was four years old, maintained perfectly, with less than 1,300 hours total time.
Bottom line is a standard Falcon 50 can do everthing a 125-800 can do, a 125-800 cannot do everything a Falcon 50, let alone a 50EX, can do.
Oh, and when you are going from Midway Island to Guam at night, those three engines make you feel a hell of a lot better.