It depends on the conditions.

If you're on the same fresh house shot each week and don't see big transition, small separation is probably fine.

Hi - I researched Bowling This Month on the 3 balls. The Hustle is considerably weaker than the  Axioms.  Your solid / pearl combination is reasonable.  Just do surface changes.  Less grit, or extender,  for the pearl to push it further down the lane.  To really answer your question we need more information about your game.  Gold Coach ABE, Denny O'Neill   

If I was to take 3 balls to a league that I bowled regularly, one would be a plastic spare ball, one that would fit the normal condition I experience at that location and the third would be for a condition that gives me the most trouble.

If that trouble is with not being able to get the ball to react because of too much oil I would take what I feel was a strong oiler. If dry conditions might give me problems then a ball that could handle that.

I would have a fair amount of separation in the balls feeling that I can adjust my line and speed enough to handle minor differences in conditions.

Once I have a good look with a ball I have always been a bowler who prefers to adjust my line/game to the conditions rather than change balls so I like a significant change if I decide to pull a different ball.

Hi - I agree with Avabob.  But,  knowing the Dual Angle Drill pattern for each ball helps in the ball decision.  Strikes and spares -  Coach Denny Silver Level / Gold Level ABE

It depends on the conditions.

If you're on the same fresh house shot each week and don't see big transition, small separation is probably fine.

Second that. If you know what to expect, a small arsenal should suffice. Things might be much different when you have to play somewhere else, with no opportunity to try out the lanes except for some warm-up shots. Then I'd put a true oil ball in the bag, and two go-to balls with quite different reactions (e.g. a polished one drilld for length and something matt with a more arcing, earlier rolling setup). Personally, I also always have a urethane ball (with a true core and a strong layout) in the bag, because with my lower ball speed dry lanes are quite challenging for me.