Is climbing easier on a light road bike or one with lower minimum gearing?
Lower gearing (or gearing in general) is generally more important than the bike weight for climbing (for most riding as well, sans high level racing). Both of the gear choices are pretty low and you'd need a pretty steep hill (or towing a lot of cargo) in order to need the lower gear over the slightly higher lower gear. As Criggie points out, there are other factors to consider other than weight -- ergonomics, build quality, etc. which can have a more profound effect on how you ride.  

A difference of 2.5 pounds is easily within the fluctuation range of your weight over the course of a few days, and is likely on the order of a percent or two of the total bike+rider weight anyway so you can basically ignore it.

As the comments say, you can switch your gearing in the back fairly easily, but this may require a new derailleur depending on capacity and cog size limits and a new chain (this is a relatively easy replacement). Note that you have to give something up for a fixed number of cogs and different gearing combinations (such as the spacing between shifts, max or min gear). So, if the largest cog is 32 in one case and 28 in the other and they have the same smallest cogs, you'll likely have bigger spacings between shifts on the larger cog one. Ideally, you'd try them out and see what you like better.