Do you have a photo of those? I don’t remember a Hollowtech square taper. (although IIRC the splined ones are Hollowtech II)
The first thing I would question is that it’s the taper/crank interface. That doesn’t click. Either the crank flops around or you’re good to go. Usually clicking is the BB moving around in the shell or a million other things that are really hard to track down.
The outboard bearings have their pluses and minuses. They’re very easy to work on and require very little in the way of extra tools. However there are reports that the bearings don’t last as long. That hasn’t been my experience but I won’t argue with it.
I’ve always felt the Shimano splined BBs were the best thing going. Less tricky interface and lasted for years.
So, to answer your questions. Maybe. I imagine some splined stuff is out there for cheaper and I’ve always thought better. But then again I don’t think the square taper is your issue to begin with in all of this.
No way to tell if things will change in a year or two or not. Probably not as both Campy and Shimano released their top ends recently. When Tiagra goes outboard, might be time to change.
For most outboard bearing setups you only need allen wrenches and a tool to tighten the bb into the frame. That tool should be included if you buy new or you should be able to get one from a shop since they come with the BB. (eg they’ve got ’em laying around) In that regard the newer BBs are really nice.
No, they don’t perform any better. They’re a less tricky interface to deal with. Square works really really well but you’ve got to torque it right (hard) whereas you still have to torque the outboard designs but to a fairly low, easy, spec.