It doesn't really make much sense to compare xlwings with PyXLL, as they perform a slightly different function and actually could be used together.
PyXLL is more comparable to ExcelPython[1], which is open source does a similar thing (enables you to write UDFs in Python). ExcelPython hosts the Python process outside the Excel process but it
a) does not restart the Python process with every UDF therefore has good performance
b) does not require any registration of COM servers - therefore doesn't require admin rights
c) does not require an add-in (there is an add-in, but it just facilitates development, it's not actually required to use the resulting workbook).
Comments
It doesn't really make much sense to compare xlwings with PyXLL, as they perform a slightly different function and actually could be used together.
PyXLL is more comparable to ExcelPython[1], which is open source does a similar thing (enables you to write UDFs in Python). ExcelPython hosts the Python process outside the Excel process but it
a) does not restart the Python process with every UDF therefore has good performance
b) does not require any registration of COM servers - therefore doesn't require admin rights
c) does not require an add-in (there is an add-in, but it just facilitates development, it's not actually required to use the resulting workbook).
[1] https://github.com/ericremoreynolds/excelpython