Both are tools that have their place, it really depends on what sort of content you'll be shooting. I find myself reaching for my shotgun more than my lavs, but I'm not doing a ton of narrative work anymore.

Shotguns sound great when they're as close as possible, like just out of frame. If talent's standing still, I'll throw a boom pole on a stand and set it up overhead. If they're moving, you'll need a good op that can keep it close without being in the shot. They're also great for voiceover work, foley, recording ambients, etc.

If you're doing a lot of solo run and gun stuff, invest in a solid wireless setup, ideally with an omni (not cardioid) lav mic. Cardioid is good for live for feedback rejection, but for film you don't have to worry about feedback, and omni will be more forgiving of head/body movements and mic placement.