About 8 years ago I started with Golden Cheetah at the recommendation of my son who was a collegiate racer. It was a reasonable start, but its documentation was poor and I felt it worth it for me to spend the money for WKO.
Once TP offered an online version, I also starting using it and quickly upgraded to TP Premium. I find that TP Premium is great for daily analysis, especially for its PMC chart, ride/segment/ride section analysis, and peak #s. However, for more serious analysis, including being able to compare performance over multiple periods, it pales in comparison to its big brother, WKO. [Fortunately, data uploaded to TP syncs with WKO]
One downside that @WindWarrior mentioned that I’d like to highlight: WKO has evolved over 20+ years. It is super feature rich. However, it not designed from a modern UI (incl ease of use) perspective, and hence has a significant learning curve. This is probably the #1 reason that is used by pro coaches (i.e. they have the time and detailed data analysis really matters) and prosumer users and doesn’t have broader appeal.