Glass arrives as a rectangle. Walls in a house that has settled for fifty years are not rectangles, and the gap between those two facts is where most enclosure trouble begins. The choice between frameless, semi-frameless and framed follows from two questions: how much of that discrepancy each system can absorb, and what is going to hold the glass up.
Frameless glass transfers its whole load into the wall, so the wall has to have been built for it. A 10 or 12mm panel is heavy, and it hangs off two or three clamps or sits in a channel fixed through tile into whatever is behind. Fixings that rely on tile and drywall will move, and once a clamp shifts the panel is out of alignment and stops meeting its seal. The answer is solid blocking let into the studs at the clamp and hinge heights, which has to go in while the walls are open, months before anyone measures glass.
Plumb tolerance decides the system as much as budget does. A framed enclosure carries an aluminium jamb up each wall that can be packed and adjusted, so it will close out a wall several millimetres out of true. A semi-frameless unit uses a header across the top to support thinner glass and keeps some jamb adjustment. Frameless has almost none: a panel set against a wall 10mm out over two metres leaves a wedge-shaped gap no seal will bridge. Either the wall is made plumb before tiling, or a channel is used to conceal the discrepancy, or the frameless look is not available in that room.
Seals are directional, which is where enclosures are most often got wrong. Sealant at the foot of a panel belongs on the outside face only, so anything that tracks behind the glass drains back into the shower instead of sitting against the tile edge. A drip rail under a swinging panel is angled inward for the same reason. And templating happens after tiling, against the surfaces the glass actually has to meet.