We should definitely not forget Fryevia. Orlandeau is definitely easier to work with, and everybody has him as their friend unit (so its easy to chain), but Fryevia's damage output is easily far superior to Orlandeau's, and her hybrid damage is useful against enemies with physical resist (such as Maxwell ELT trail, and that last Wilhelm event).
The problem with her is that she's difficult to build (requiring four Letter of Arms TMs), dual wield, and her sword (the TMs you build for Orlandeau at least can find wider usage on other dps units). Worse, you really need more than one of her (meaning yet another TM array grind) and maybe even an extra friend unit to chain.
Orlandeau is easier all around, especially if you're not a whale or don't do TM macroing, but Fryevia is still the better BiS unit.
In terms of ranking Orlandeau, Aileen, and others, for GL we shouldn't follow JP's example unconditionally. By delaying some units, nerfing TMs and stacking, and adding some excellent exclusive units, the dynamics are very different.
Reberta is also an amazing unit (but again, you really need more than one of her to shine). As is Olive. Aileen's meta also changes due to Yun's TM crimson slayer, especially later with Aigaion's arm.
By the time that GL catches up with JP, I expect the meta to have diverged significantly.