I feel like this video explains it pretty well. 

 

Right or Left-Handed Fishing Reel: Which One is for Me? | SportRx - YouTube

 

But in reality, it's all a matter of preference. Which side is more comfortable for you?

Watched the video.  So, just switch before the lure lands.

2 hours ago, J Francho said:

Watched the video.  So, just switch before the lure lands.

Yep. Or, just get the type of reel opposite to your hand (e.g. I'm right handed, so I'd get a left-handed reel).

I use both right and left handed reels. I pitch right handed, so a lefty works better for that. Most guys I've fished with learned to pitch left handed. 

Not always. Depends on the reel. 

3 hours ago, BaitFinesse said:

You still have to switch grips from casting to palming the reel even when reeling left handed.  Switching grips is essentially the same thing as hand switching.  

Nope. Left hand is on the butt. Right is gripping the handle below the reel. Thumb is on the thumb bar and spool. I cast, grab the handle with my left, then climb/slide right up to palming the reel when I start to crank. I'm engaged instantly and never lose contact. Like a ninja.?

Same here.  I taught myself to cast with my hand in reels my position.  Makes everything smooth and easy.  

On 2/9/2021 at 6:22 PM, BaitFinesse said:

Meaty section of hand/palm the thumb grows out of.  Whatever that's called.

This is probably due to gripping the reel tighter than you need to because you aren't quite comfortable yet and less about conditioning. Tightening up everything from one's pucker to one's extremities is common before coordination kicks in. Try softening up a tad by relaxing your core, lower back and neck, or any other parts not associated with the task. Doing this is contagious, and you won't be as tense.  This will delay fatigue and shorten the learning curve.