For a small Vin-Vout difference, is it worth using an LDO vs a buck regulator?
Dropping 5 to 3.3 V at 250 mA will mean having to lose 0.425 Watt in the LDO, you will need a massive heat sink to make that work.

An LDO will never be more efficient than a buck converter, unless you need so little current that the power used by the regulator itself becomes an issue.

I have a mis-designed PCB right now where I tried doing exactly what you are proposing to turn 5 V into 3.3V at 200 mA and even though I have a large'ish copper plane as a heatsink the LDO still reaches 80 deg C in a few seconds.

I'm currently redesigning my power supply to use a MC34063A converter in stead.