In my tow fleet of 6 we have no carrier rollback flat beds. I see all the so called need but a set of dollies and my regular tow truck boom, and all does the job just fine. However so many call a rollback a tow truck when they are not a tow truck but a carrier. I personally will not own one. They are too limited in their abilities. As far as recovery sure the rollbacks can do that sort of until they bend a bed, the process, why not just have one truck that can do it all? So I ask you all, which do you prefer I'd be interested in knowing. I'll share your comments on my TV show. Truly the AyreWolf
If i could only have one... I'd have to take the conventional because, as you said, there are some things you just can't recover effectively with a carrier. But, The carrier is sure great in many situations.
Many drivers don't remember the days when there were no carriers. We did it all with a conventional truck.. 
If only someone would build a hydraulic version of the good ole Holmes 500 that I use. Outside of one HD Rotator we do not have any other hydraulic tow rig in our fleet. Of them all the 500 Holmes still remains king as far as medium to light duty tow units. Just look at the picture of my personal truck yes that is a 500 Holmes and it out works any hydraulic.
I think it depends on the type of work you do and the area you work in. In my business I run alot of doubles and you can't do that with a conventional truck. I also do very little to no winchouts because I'm not on a rotation list getting those types of calls. I do own both and my wrecker sits unless I get a call for something to big for the rollback. Also in my area there is alot of 4x4 and all wheel drive vehicles that people demand the rollbacks for and they are scared of someone with a wrecker will tear of their vehicle so they request the rollback.