I operate a military transport with TCAS II. We always use TA/RA whether VFR or IFR.
On several occasions (both VFR) I have responded to an RA that I would have hit had I not done so. Had I been operating TA only, the time it takes to identify & locate the other aircraft may have been fatal.
Beags - If you operate TA/RA, you can manouvre as required, even ignoring the RA if you have the traffic visual and you decide the RA puts you in greater danger. If you operate TA only, you may never get the opportunity. Have there been any crashes where the response to a RA caused the collision? I bet there are plenty where use of TCAS RA mode would have saved lives.
If the RA traffic is below you, or outside your FOV, then RA is the only protection you have. If flying VFR, you should be able to monitor the airspace in front of and above you where TCAS will ask you to fly.
Flying has inherent risks. The open FIR can be a nasty place, where not everybody is playing by the rules. If it was mandatory for ALL taffic, including gliders to squawk mode C, it would improve matters. Cost should not be an issue when safety involved.