For general purposes, I would stick to the incendiary types for three reasons:
1) Unless you plan on using them on a regular bases and rotate the batteries or store them with lithium batteries, chances are when you need them the device the most, the batteries will be dead or may have leaked out, damaging the light.
2) Since most of the electronic versions are dependent upon the ability to send out a “flash” to get your attention, I think that unless it is using a strong strobe, during daylight hours it will be essentially “washed” out. This would especially true of LED versions, which would be better seen during evening hours.
3) Cost and disposability; I would suspect that any of the electronic versions that are worth anything, are high-end devices. If they become damaged or lost, you could be out of some serious cash. The incendiary flares are relatively cheap and are intended to be disposable. They also have the potential of being used to start a fire in adverse weather conditions.
I am sure there are other opinions out there, just my 2 cents. Pete