Which to choose? Is it worth spending the extra on the Solution (2nd hand) or just go for a new flexee - will be for backing a youngster and for the foreseeable.
Try them both and see which you personally like. I liked the Solutions, don't like any of the HMs. I know you can trial the solutions, not sure about the flexees, (I just rode in someone elses).
If you want a synthetic FlexEE, move fast, she's announced today that they're not profitable enough to continue with and are being discontinued. The leather FlexEE is being launched at YHL, but it's around £700.
You can trial the FlexEEs too. Definitely try and see what suits. I love the Vogue and don't mind the old Fheonix. I don't dislike the FlexEE but one of my mares (typically the youngster it was bought for) didn't care for it at all. Still not quite sure why, but I sold it to a friend who is now backing her youngster in and both are getting on fine.