The first question is movement load, not view quality
Families often start with the idea that window seats offer better scenery and aisle seats offer easier access. For seniors, however, comfort is often decided by the repeated actions of standing up, turning, sitting down and doing it all again.
A good seat is the one that makes the day's most frequent actions lighter.
Window seats are often steadier on longer or more winding road sections
For seniors who feel motion strongly or like to lean and rest, a window seat can provide a clearer physical edge and more support for the upper body. That can reduce the sense of being jostled around on longer road sections.
This works best when another traveller can help with water, jackets and small items so the senior does not need to get up repeatedly.
Aisle seats usually work better when movement and access matter more
If a senior needs to stretch, adjust position, visit toilets more often or get in and out frequently, an aisle seat is usually easier. It removes twisting and the need to disturb others every time they move.
On a day with many stops, that small advantage repeats enough times to become a major comfort gain.
The strongest setup is changing the seat with the day's job
A long transfer day may favour a steadier window position. A stop-heavy day may favour the aisle. Mixed-age groups usually do better when seat choice stays flexible instead of becoming a one-time rule for the whole trip.
Treat the seat as part of the daily plan, not as a permanent label.