The problem with Siglent SDG2000X series is that it has only one Aux In/Out BNC, whereas a proper generator should have Sync, Modulation, Trigger or even more BNCs for each channel. DG800/900 is a little better, with two BNCs, one for each channel. Keysight 33500 series has three auxiliary BNCs.
And what is it with these generators including a counter? I understand its easy to implement a crappy counter, but why waste a BNC for it? Except for the most basic models, I don't imagine it would be a selling point. Better to use that BNC as a trigger or another function generator control.