Rich, You've received some great advice from folks here. I wasn't familiar with the Shower Buddy. I'm impressed. That certainly looks like the ideal option for PALS with a tub. If you do go with a roll in shower, I recommend at least checking out the Rifton HTS (adult version). I've attached a picture of my wife's well worn chair here. We received it as a 'loaner' from our ALS Center. My guess is that it might be more comfortable than the Shower Buddy, but not sure. We used it for between four and five years, from when my wife first started having challenges getting up from the toilet up to the day she passed away.
One key feature we liked/required was that the back of the chair tilted up, in addition to tilting back. We did a stand and pivot and that was crucial to bringing her to a standing position. It also helped for setting her down in the chair. Once seated, we'd tilt her back to a more level position. Even for folks who will eventually hoyer, that tilt feature should come in very handy pre-hoyer. And then you can hoyer into it just like with the Shower Buddy.
We found a pretty thin, U-shaped, padded fabric seat cushion that was easier on her bottom than the plastic. My wife went to the bathroom several times a day in the chair, right in her room. We could take the head rest off easily to cut her hair. We rolled her into the shower for actual showers, setting her ventilator on the toilet and being vigilant keeping water away from the trach area.
Like Fusia, I recommend a heated floor if you can pull it off...no biggie if not.
All the best...Jon