Unless there are unusual circumstances, I'd steer you toward a conventional 2 pc ramp in .45 ACP pistols, regardless of length. Smaller calibers can go either way, although I personally prefer ramped barrels in .40 and smaller.
A .45 spec feed ramp needs to go deeper (.400" or more) into the magwell from the top of the rails than any of the ramps go (.315" typ.) in ramped barrels. This makes you have to blend the barrel's ramp back into the frame's ramp to keep optimum feeding. By the time you do that and keep a reasonably similar angle to the ramp, you loose most if not all of the support at the rear of the chamber that the ramped barrel theoretically gives you.
So even with a ramped barrel in .45, you usually wind up still with a 2 pc feed ramp, just jointed in a different place.

And it took more work to get the same end result.
If you have an alloy framed .45, the better way to get a steel feed ramp is to install an insert. These typically go .500" deep from top of the rails and will give a complete steel feed ramp, where the ramped barrels would be partial.
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