Depends entirely upon the nature of the mod in question.
If I can stick a specially named file on the root of the SD that the burned in silicon will load without question then the hard mod had better do something seriously special (overclocking, more processing, dual nand where a virtual one is harder, shared nand, rapid fire buttons, easy access to something I might not have access to, debugging capability and so on) for me to consider it.
As that is unlikely to happen in the modern world we are back to considering what goes. We might also have to consider the nature of any support for them but I will assume it is acceptable.
Hardware mods. Traditionally a bit harder for device makers to work around which seriously lessens the "my little brother updated" type thing. If they come with perks like those mentioned above then so much the better.
Software mods. Their only saving grace is being software you can mostly download it for free (there are things that you get to pay for from time to time, sometimes because the people doing the deed are using lots of computing power to make something, other times because the people doing the mod reckon they can get away with it which I guess is fine as well). I don't particularly consider soldering and related activities that troublesome for most of the things out there, would prefer not to have to hook probes onto a BGA though or remove epoxy in some cases.
Really though until we know more about the attack surfaces of the switch and how things will play out it is all basically complete speculation that helps nobody. Such things are a bit of a spectrum anyway -- the average 360 DVD mod could be done on some fairly popular motherboards with a sata lead and then assembled back again, however as it involves pulling something apart it was still hardware according to some, compare that to some of the later RGH stuff where you had to run wires around certain locations to avoid inducted noise... it is not even close.