best bacterial expression system?

[AShaw5]

Aside from the concerns about the small size of the peptide, I have used
both systems and would suggest staying away from the His-patch system.  In
our hands, insolubility was not improved by moving to the His-patch
system.  What also bugged me was the construction of the His-patch.  I
thought that I would be able to use denaturing condition to purify the
protein on Nickel columns but if the protein is denatured, the His-patch
is also disrupted and purification is impossible.  I wasn't impressed with
this system.

Andrey Shaw