Quote from: PCW on November 26, 2019, 01:33:47 PM

Q: What would be the advantage of using "2" addresses on Testnet rather than "m" (and then all "3" addresses on Mainnet rather than "1")?

depends on the script you're paying to

P2SH (starting '2' or '3') can be used to pay coinbase (or any ouput) to a segwit script. Or any script.

It can also be used to just pay to a public key hash. There's no real need to do this, unless you're paying some novel type of public key hash that isn't supported by your wallet software directly (a nice forward compatibility feature). You can simply use a regular P2PKH address, and get an identical outcome (although a desirable property is that for today's blockchain, you improve other people's coin's fungibility if they are using P2SH, but it somewhat deteriorates your own coin's fungibility...).

Another way to look at this would be at the network level. Which type of addresses are most common, '1' or '3'? I believe the answer, today in November 2019, is the '1' type, so there is no fungibility advantage in using P2SH. But that may change in the future, and the fee weighting of segwit encourages P2SH wrapped segwit outputs more than legacy P2PKH. Native segwit addresses have the same fee weighting discount, but are inherently smaller on chain than either P2PKH legacy type ouputs or P2SH wrapped segwit outputs.

So if you're going to keep your mined block reward a long time, using either P2SH wrapped segwit addresses or bech32 native segwit addresses is the prudent option. Looking at coinbase transactions today, many miners are indeed using bech32 native segwit addresses for their block reward (but it's impossible to tell whether P2SH addresses are wrapped segwit or not, as the script that the output is paid to is publicly unknown until the coins are sent from that address)