It's just my opinion, but I'm not fond of the third-party Saturn carts. The official memory expansions and save carts had tapered cart edges that eased into the slot, whereas the Gameshark and the 4-in-1 carts have square edges that are rougher to push in. If you're not inserting and removing cartridges all the time then it's not a big deal, but if you plan to swap out the cart a lot then I'd recommend you do the switch mod if you really need to play imports on a western Saturn unit.
The Saturn cartridge port is crap anyway and probably will break if you keep swapping cartridges, so I'd go with what he said, or just buy a 4-in-1 and let it sit in the cart slot for all eternity like I did.
You don't need a chip to play imports, it's just a jumper swap. Forgive me shilling for the site, but GamesX has a pretty comprehensive write-up on the mod: http://www.gamesx.com/wiki/doku.php?id=imports:sega_saturn