I am not sure if this helps or not, but it probably depends a lot on your use case.
I have both the stihl brush cutter (straight shaft with bike handles and back pack straps, and separately I have the stihl pole pruner. They are both great tools and when you need them it’s helpful to have in demand.
I considered a combi (that’s what I went to buy actually) when I bought them. The reason I did not come home with the combi was that the unit I demoed it felt like their was some sloppiness to the heads/individual implements vs the individual tools which everything was fixed and solid…and in my mind I did not want loose tools at my feet or overhead. The dealer suggested what I was experiencing was not normal and something needed to be fixed. They genuinely tried to not sell me two tools. Right or wrong I went individual tools.
that being said I use the pole pruner much less compared to the cutter. Looking back I wish I was patient and would have asked to try another unit even if I had to wait a few weeks.
If I thought the implements connected securely I (think) would prefer the combi.
As far as the brush cutter mine has a guard, but that only holds down some of the debris. (If you plan to use the cutter with shorts and crocs on, you may have unpleasant experience
). Sounds like you have the gear so I think you would be fine with whatever you choose. I think it would be difficult to catch your foot with the tool…I’d say there is a better chance your shaft is too long and you have to adjust the handles down to your height(assuming the combo has the bike handles, but I don’t know that).
good luck. I hope this helps.