FMQ notwithstanding, there is one place a vertical bobbin is easier to deal with:

If you get a rather majestic birds' nest and the machine freezes, most of the time you can get at the threads by pulling out a vertical bobbin, snipping the threads you can reach, then removing the quilt. Drop ins with that kind of snag can be a bear to deal with.

I've used both types and prefer the vertical. The Brother 1500 and the Juki 2010 are both vertical. So is my Pfaff 2170.

In my experience with everything from an old Singer treadle, 80's machine, up to computerized machines..you can easily FMQ on all of them. It's a matter of getting to know your machine, what threads and needles work best, and what speed to go at. Eyelashes are most always caused by upper thread problems..either not put through tensions discs properly, or could be as simple as your machine just doesn't like that thread. On the non computerized machines...moving your hand too fast will cause eyelashes..try slowing down..a lot...see if that helps..if it does, then it's you...you need to find a rythm for that machine..if it doesn't help, then rethread, try again..slowly..if that doesn't help..try an entirely different thread. From all the people that I see, their biggest problem is speed...they watch the videos of the longarmers going 90 miles an hour...you need to slow down,,slow down...slow...till you get the hang of it...then you and your machine can get into a groove. Good Luck!!!!!!!

Used to get eyelashes on my Viking Sapphire 875Q but have learned that if I set the speed control down to the second or third notch from the bottom (on the screen) and move the fabric slowly (you need to test what slowly means to you!) I never get lashes anymore. Knock wood!