Custom sport 9mm barrel and regular 9mm barrel are the same as far as I can tell. I think the "match" is the longer barrel and weight added to a Custom Sport. They are both 9mm barrels.
the good thing about HK USP's are the number of Variants you can have, as well as switching parts to make different variants.
IE; if he had a regular USP Variant 1, and added the factory option tuning package (match trigger and sights), it would then become a Custom sport; which is available in 9mm, .40. (.45 is available, but conversion may not be possible, as the .45 frame is larger)
*All USP's are available with tritium sights in three dot configuration.
*Conversion kits are available for all USP's to convert from one 9mm to .40, from Expert to Elite, to Stainless, to match sights to jet funnel or no Jet funnel (no JF for Production though)
I performed the LEM Conversion on my first USP, so it is now a DAO.
My Custom Sport may become a stainless, as the USP stainless can have the Tuning package of Match Trigger and sights as an option.
My current USP 9mm Custom Sport is also now a variant #3, no external safety; the lever is for decocking only
here is a link;
http://www.heckler-kochjs.de/defaul...lJmhlYWRlclBpYz1oZWFkZXJfYWt0dWVsbGVzLmpwZw==
Check the accessories page, The tuning package is only listed on the German Language site. The details of the conversion kits is listed after details is clicked for each pistol.
I hope this is usefull for anyone with questions about conversions.

, as well as factory options.