The 5 wood and 3 hybrid are not really the same. The 3 hybrid is comparable to a 7 wood (see Ping's website for example). The hybrid is more forgiving due to the shorter shaft and therefore easier to hit as a result. In the end it all comes down to how far you hit each club and if you are getting similar distances go with the 3 hybrid as it will likely be more consistent. Good luck - I can relate as I carry both and am trying to find a hybrid to allow me to drop the 5 wood if possible or at least swap them depending on the course.
5 wood vs. 3 hybrid - Page 4
I Agree a 3 hybrid is'nt really filling in the gap as most 3 hybrids are 21 sometimes even 22 degrees so it would'nt really be suitable to fill the gap. I find a 5 wood with a relatively shallow face would be best as it is still going to let you hit out of the rough easier and can obviously still be used off a tea and fairway. I find the Mizuno F-60 and Ping G10s good 5 woods overall. However with all this said there are a few long 3 hybrids out there that you could use. It just depends on preference.