Bicycle Mechanics - BB sizing when 2 lengths spec'd?

I'm looking at the Sugino XD600 for my wife's bike, and it lists 113/118 for spindle lengths. How do I know which I need?

Here's the relevant info (do you need any other info?):
early 1990s Giant Innova hybrid
7sp, 135mm rear hub
Tubing is not oversized

I believe the 113 is spec'ed for a 1-1/8" diameter seat tube (older steel frames) and the 118 mm is spec'ed for 1-1/4" and 1-3/8" diameter seat tubes (almost all Al and Ti and many newer steel frames).

The longer spindle is needed to get the crank far enough from the seat tube that the front derailleur can reach to small chainring before it hits the seat tube. This is a particular problem with triple cranks.

You need the 113mm for the 1 1/8" and the 118mm for the 1 3/8" the 1 1/4" can use either BB spindle lengths.

As others have indicated, the longer spindle length is typically for bikes for larger tubing which will move the front dérailleur outboard.

I believe the 113 is spec'ed for a 1-1/8" diameter seat tube (older steel frames) and the 118 mm is spec'ed for 1-1/4" and 1-3/8" diameter seat tubes (almost all Al and Ti and many newer steel frames).

The longer spindle is needed to get the crank far enough from the seat tube that the front derailleur can reach to small chainring before it hits the seat tube. This is a particular problem with triple cranks.

I've heard a different story that makes sense to me: The different spindle lengths correspond to the rear dropout spacing 130 vs 135. Using the wider spindle length with 135 dropouts corrects the chainline.

I've heard a different story that makes sense to me: The different spindle lengths correspond to the rear dropout spacing 130 vs 135. Using the wider spindle length with 135 dropouts corrects the chainline.

I'm going by what I read in Campagnolo's installation sheets and on their web site. They differentiate between required bb spindle lengths by the diameter of the seat tube.

I'm going off what the Quality Bicycle Parts Catalog had to say.