SQL Server options that influence log buffer flushing or commits-per-second performance?
both running identical hardware (VMs)

If the performance of this minimal test is that drastically different, and you have thoroughly confirmed that the software (and instance / database level settings - for example the checkpoint-related settings like indirect checkpoint, recovery interval, target recovery time, etc might affect a benchmark like this one) is the same, then the statement about the hardware being the same is probably not exactly right.
You mentioned WRITELOG is your highest wait.  With this workload, WRITELOG will almost inevitably be the highest wait, since that's all you're doing.  Is the difference in WRITELOG waits between the two servers large enough to account for the 10x difference in transactions per second?
If that wait is significantly higher on the slow server, then it's possible that, despite the same hardware specs being specified at the VM level, the &quot;path&quot; to the I/O system is slower on the second VM.  Or the underlying storage is slower.

Check out the sys.dm_io_virtual_file_stats DMV to see if the slow server is experiencing slower writes or more frequent / longer stalls than the fast server.
Check the SQL Server error log to see if there are any &quot;SQL Server has encountered X occurrence(s) of I/O requests taking longer than 15 seconds to complete on file [M:\SomeDataFile.mdf] in database [SomeDatabase] (5).&quot; error messages.

If you're seeing slowness reported in those places, you'll need to work with the VM administrator -  to see if there is a difference in the underlying storage, or the access to the storage (if it's going out to a SAN).