For Spyderco folders I find their serrated edges are generally much sharper than their plain edges (you can see that in the much taller bevel height, even if it is just on one side), so I only own and carry fully serrated Spydercos (and only Civilians, but that is another matter).
I have almost never seen a plain edge folder that was sharp enough as a plain edge from the factory, usually they are out to a useless 15-20 degrees per side, almost always opening gradually the edge angle to even far worse angles towards the tip (25-30 per side near the point is common)...
Re-profiling a 4" blade freehand is dicey, as on a folder the slightest asymmetry in bevels is really obvious, and worse of all the longitudinal stroking motion I use (to get as flat-sided V bevels as possible) means it is almost impossible to really have any heavy re-profiling done into the last 3/4" of the edge, so you have to leave 20-25% of the entire edge near the handle at its original factory dullness...: Keeping a 4" folder edge angle really low all the way the ricasso practically requires a guided sharpener to overcome this obstacle, since many folders do not have a deep "heel" at the rear of the edge to help you re-profile at the rear...: Such guided sharpeners have trouble dealing with fixed blades over 8-10", so they are simply not worth the investment for me.
If there is a fully serrated version for a folder, that is always what I would choose, as they are good to go from the box (a huge relief!). Another huge, huge advantage of most factory serrated edges is that they keep the same one-sided bevel geometry towards the tip, and for that reason alone the knife is often much sharper towards the tip than a plain edge, especially a deep bellied plain edge...
The thing about serrated edges is that, when worn, no matter what anyone says, they will never again be restored to full factory sharpness (unless sent back to a manufacturer who will do this), so they only make sense if you rarely use the knife, but need it to perform superbly in an emergency.
My favourite serrated edge story was from a factory worker who had his jacket caught up in some heavy machinery that was dragging him into its maws: He said that if it had been a plain edge he would have been dead.
Gaston