They are totally different things.

Trainerroad gives you realtime graphs to look at while you follow some training plans it has (which are very similar to plans you find in many of the go-to training books you can buy).

Training peaks is an analysis software, which has features similar to WKO+, golden cheetah, and now strava premium.

You need something to track fitness (I use WKO+ and strava premium), and if you're on the trainer, you need entertainment (I use videos or a 3D VR Trainer workout program, you could use videos and trainer road).