For the record, in 22 years of work with inflight icing. I am not aware of any icing-induced accidents or incidents that involve a properly functioning TKS system, There have been some events that involve a clogged system.
The same cannot be said of boots. Westhawk makes excellent points regarding operation and maintenance. However, a boot system will typically require several cycles to optimally clear the ice off the wing and keep it that way. Even when operating correctly, a boot system will likely leave some residual ice on the wing and there will always be inter cycle ice. These can be critical, and there is no such thing with a properly operating TKS system.
That said, there is the problem of fluid supply and proper maintenance with TKS.
In the end, a hot wing trumps all, but you will find that some manufacturers recommend operating the hot wing in a deice, as opposed to anti-ice, mode. I don't care for that...it leaves open the question of detection and inter-cycle ice... but when you dial back the available thermal energy, a hot wing runs wet instead of fully evaporative, and this generates runback ice. There have been some problems with that occurring in front of control surfaces. Using it as a deicer is supposed to improve that problem.