I am a former turbo prop training captain who, many years ago, faced exactly the same dilemma. I had the choice at the time of going on a Boeing 737 or an Airbus A320 as an FO. After a lot of heart-searching, I took the Airbus. Anyway, the rest is history. I have now been an Airbus training captain for many years.
Basically, I can only second and third all the comments made here. However unfair it may be, no one cares about turboprop time – it is essentially time in the lay by of your career. Without a Boeing or an Airbus on your licence, you are extremely vulnerable to the ups and downs of life. It is terrible to say this, but you’re basically considered a pilot who has not quite made it. You will find, much to your horror, that a young guy or girl with 300 hours medium jet time, and 500 hours total time, will be considered way more valuable than you will be with 10,000 hours on turboprops. That is just the way the system works. Get out now and do not look back!