The Symmetros is softer and more cushioned than the FFE2 and Panthea. I find the FFE2 and Panthea very similar.
I think the Symmetros is the best for recovery/easy runs. It also works fine for picking up the pace on cutdowns or tempo or whatever since it is bouncy and a tad lighter than the FFE2 actually.
I think the best two shoe training rotation is the FRRF1 and Symmetros. FRRF1 for workouts and Symmetros for easy/recovery/ long runs.
The Panthea is probably the better long workout shoe and the FFE is probably a bit better as the one shoe rotation do it all trainer, but they are very close. I think either one would work well for someone who likes one lightweight trainer for all their training. The Symmetros fits that bill too for people that prefer something more forgiving since it is still very versatile.
Honestly, the Reebok lineup has a lot to offer overall now. They were missing a good well cushioned trainer, and now that spot is filled by the Symmetros. They could still use a max cushioned type of shoe, higher stack plated trainer and racer, less EVA rims on the floatride shoes, and no more caged uppers.
I have not tried the FRF2, but will skip it due to the gained ounce of weight. I stocked up on the FRF1 on discount.
The FRF Pro, FRF1, Panthea, FFE2, and Symmetros are all excellent. The RF London was a nice shoe too.
The FR 2.0 is a good midsole with an improved but still rough upper and too much outsole.
The Harmony Road 3/3.5 was not very good but is now covered by the Symmetros.