This gets argued as a matter of philosophy and it is really a scheduling problem. Both splits are fine. What decides it is how many days you train and how often each muscle ends up being worked.
What each one actually is
Upper lower alternates the top and bottom half. At four days a week that is two upper and two lower sessions, so every muscle is trained twice.
Push pull legs splits by movement pattern: pressing, pulling, and lower body. At six days a week each muscle is trained twice. At three, once.
That is the entire difference that matters. Everything else is exercise selection, which you can do either way.
Choose by how many days you actually train
Three days: full body, not either of these. Three full-body sessions gives every muscle three exposures, which beats PPL giving it one.
Four days: upper lower. This is its home ground and it is hard to beat.
Five days: upper lower with a fifth session for whatever you are prioritising, or a rotating PPL if you can handle non-fixed days.
Six days: push pull legs, run twice through. This is the configuration PPL is designed for and it works well, provided you can genuinely recover from six sessions.
The recovery window is the actual constraint
A muscle group needs roughly 48 to 72 hours before it can be loaded hard again productively. That number does not divide neatly into seven, which is why splits feel awkward and why the calendar week is a poor unit for organising training.
Upper lower fits it well: train upper Monday and Thursday and you land almost exactly in the window. PPL over six days does too. PPL over three does not, by a wide margin.
More on the underlying arithmetic in how many sets per muscle per week and building a split around muscle recovery.
The practical tiebreakers
Missed sessions. Upper lower is more forgiving, because the next session covers similar ground. Missing leg day on a PPL means a week without legs.
Session length. PPL sessions are shorter and more focused. Upper days can run long, which is a real problem if your window is an hour.
Fixed or flexible week. If your training days move around, rotating PPL is workable. If Tuesday is always a training day and Wednesday never is, upper lower is easier to hold.
Ready-made programs for both shapes are in free workout plans and our training collections.