"It is a tough one. IPL is obviously a great opportunity not just for guys in New Zealand but from around the world to potentially earn that money tag that can potentially set you up a long time," he said.
"The bottom line is New Zealand comes first. It is our key priority and any game for New Zealand you love playing. You are always competitive, but playing for New Zealand is the pinnacle of what you want to do."
Anderson, who first played against Williamson for Christchurch Boys' High School against Tauranga Boys' College in the Gillette Cup finals, says it will be interesting to see how Williamson goes as captain in Zimbabwe and South Africa.
"Kane has a smart cricket brain. Baz [McCullum] is one of the most aggressive captains in the world so just being around him means he will take a little bit out of him.
"Kane will think about things, process things and take a pretty high percentage option. There will be times when he will pour it on when he has to and I think it is a beauty that he is young in the whole scheme of things of captaincy.
"He is only going to get better as he goes.
"He is a freak of a player, to be fair. He is turning into one of the greats on the world stage and to see that happening in front of your eyes is pretty cool."
Anderson's main objective for next summer's home and away series with Australia is to make the test team.
"In the one-day, limited-overs form of the game, I feel really confident. I know what I am doing. I am going to make a bigger push at the test level. That is my favourite form of the game to play.
"I would love to be in that side all the time and that is my big goal."