having

```toml
[unstable]
build-std = ["core"]
build-std-features = ["panic_immediate_abort"]
```

in your .cargo/config.toml makes this pretty easy to a/b test by just toggling nightly (it's not apples to apples but maybe interesting enough for an estimate).

in a small but nontrivial example:

```
$ cargo size --release
    Finished `release` profile [optimized + debuginfo] target(s) in 0.06s
   text	   data	    bss	    dec	    hex	filename
  52968	     84	  11816	  64868	   fd64	nrf52840-eusb
$ cargo +nightly size --release
    Finished `release` profile [optimized + debuginfo] target(s) in 0.10s
   text	   data	    bss	    dec	    hex	filename
  34516	     84	  11816	  46416	   b550	nrf52840-eusb
```

in a much larger work project:

```
$ cargo size --release
    Finished `release` profile [optimized + debuginfo] target(s) in 0.25s
   text    data     bss     dec     hex filename
 157036     808   21172  179016   2bb48 REDACTED
$ cargo +nightly size --release
    Finished `release` profile [optimized + debuginfo] target(s) in 0.25s
   text    data     bss     dec     hex filename
 121992     808   21172  143972   23264 REDACTED
```