walk in shower

Long story short, I have a PVC shower pan installed with the mortar bed installed over it. I ripped out my shower curb and plan to make it into a curbless shower. I would like to seam the shower pan to a fluid-applied waterproofing membrane I plan to install over the concrete in the remainder...

My dad will be 80 soon and is visually impaired, but in good health so far. I was thinking of attempting a walk in tub install or putting in a walk in shower with a fold down seat at his place. Which is better and why? He's not a techy guy, so if there's a lot of controls to confuse him...