Which Is The Best Pokeball To Catch Suicune With?

With all the legendaries I've found thus far excluding Lugia I have used standard ultra balls. However, with suicune I know "dive balls" work quite well too which can be obtained from apricorns when taken to Kurt. I'm trying to catch him at the moment to..

By the way, when you try make sure you take like 50 ultra balls, as it will take a few attempts.
Hope I helped.

Ultra ball

If you have a lv. 100, then you can use a level ball, it works with a point range maximum of 90%.

Fast ball(Or master ball), on first turn, Or if you can use any ball, using it's ability to your advantage.

First use fast ball (from apricorn), if that doesn't work put him to sleep and down to a few HP, then try ultra balls, or if it is dark outside you should use dusk balls-(recommended method). I caught him in 7 dusk balls at night in heartgold, and 15 ultra balls in soul silver. Hope this helped :D