A small data contribution to the table: I implemented BIP-360 P2MR in Bitcoin Core on regtest and measured spends end to end, so some of the Efficiency estimates can be grounded in actual transaction numbers.
Measured with identical transactions where only the input side differs (one input, one P2TR output, SIGHASH_DEFAULT, a <key> OP_CHECKSIG leaf):
| spend | control block | weight | vsize |
|---|---|---|---|
| P2MR, 2-leaf tree | 33 B | 513 | 129 |
| P2MR, 4-leaf tree | 65 B | 545 | 137 |
| P2TR script path, 2-leaf tree | 65 B | 545 | 137 |
The P2MR witness comes out 32 bytes lighter than the equivalent P2TR script path spend at every depth (except m = 7, where the control blocks fall on opposite sides of a compact size boundary and it is 34), so P2MR effectively gets one extra tree level for the price of a P2TR script path. These are script paths on both sides: a P2TR key path spend at 64 witness bytes stays far cheaper, consistent with the 64 vs 128 comparison in the table.
One omission that may be worth a line in the comparison, since adoption complexity comes up repeatedly: implementation cost. The consensus delta for P2MR as specified is ~96 lines on top of Core’s existing taproot machinery, because witness v2 reuses tapscript execution, the BIP-342 sighash and the Merkle walk unchanged; only the commitment check differs. Of the types listed, P2MR (and P2QR, which shares its structure) is the only one that is nearly free to implement given taproot; P2TRH and PKR need a BIP-340 variant, and the new witness styles need serialization and P2P changes.
Happy to measure other configurations on regtest if concrete numbers would be useful here.