Spline vs. Tongue & groove

As a novice woodworker I'm trying various methods. A while back I used a slot cutter and spline material to join two pieces of plywood on a long edge. It worked well. In my current project, a desk-side table with two shelves, I sought to edge the 3/4 plywood with 3/4 pine and I was determined to accomplish it with a tongue and groove joint using the same 1/4" slot cutter. I'm getting it done, but it seems like a lot more effort in both measuring and setup than simply running the same slot in both plywood and pine, and then fitting the spline. To do the tongue I ran a rabbit bit and had to set separate heights for the face and back of the pine because it is a little bit thicker than the plywood. I was thinking about ordering a matched set of slot cutters (one for the groove and one for the tongue), but that brings me back to the simplicity of the spline.

So here are the question for you more experienced woodworkers:

1. Is tongue and groove superior to the spline?

2. If the spline is just as good, is MDF acceptable or should I use plywood because it's surface adheres glue better? If so I think I should get some plywood sized slot cutters.

Thanks in advance.

Art