The only person who can answer your question is yourself. How much oil to you bowl on regularly? If it's a lot, then go with the Passion or Vertigo. If it isn't really heavy, only moderately heavy, then you might look at the Black Widow. If it's primarily medium oil, then go with the Agent. Of the balls you mentioned, you can probably get the Vertigo for the cheapest, just because it's being discontinued, not for it's performance. On most house patterns, you rarely need a really heavy oiler. Just depends upon where you bowl.
All are very good bowling balls. You won't be disappointed with any of them, provided they are used on the conditions for which they are designed. I will say this however, the advertisments for the Black Widow do mention that it is designed with a cover that is easily altered to fit lane conditions.
Chuck
Edited on 6/14/2006 7:35 PM