Basically a swim jig, spinner bait, swim bait all are supposed to imitate a bait fish swimming. Alot depends on how you want to make the presentation, fast slow, water clarity, more or less vibration etc.
A swim jig is basically a spinner bait with no blades. I prefer swim jigs myself over spinner baits. They come through the water easier and are less work for me to retrieve. Swim jigs have a lead head thats painted, weed guard and a skirt that is tied on.
Here is a swim jig
A swim bait is a soft (most of the time) bodied bait that has a paddle tail and imitates a bait fish. They can be hollow, solid, fished with a jig head, weightless, swim bait style hook or texas rigged.
Here is a swim bait
I fish jigs about 90% of the time year round. My prefered method is to pitch or flip a jig, but alot of times, swimming a jig is better. For that I prefer the Flip N Swim jig from North Star Custom Baits. its a hybrid swim jig and flipping jig in one.
The main difference in between a swim jig and flipping jig is the nose of the head. A swim jig will have a more pointed arrow dynamic head. This helps in coming through grass and weeds much better. You would want to use a swim bait style trailer with a swim jig. Curl tailed grub or any type of swim bait style trailer will work great.
I like to take my swim jigs and use them as a search bait. They can cover alot of water very fast. Cast out to an open spot to start with, let it sink for a 3-4 count and start your retrieve. If your trailer has a lot of action, you can just reel it back in. If it doesn't, vary your retrieve, giving it a few bounces etc. Find some cover to throw it into as well. Bounce it off logs, brush etc.
With the flip n swims from North Star, you can also pitch the jig into cover, let it sit and swim it back. very versatile jig.
Hope this helps some