I'd go for the 2.6Ah personally. Obviously the 2.6Ah will last twice as long. But the charging time with an intelligent jobbbie would probably be the same for each battery capacity? My Makita 3.0Ah takes 20 minutes to recharge so it's cup of tea time when it dies. If I had gone for the 1.5Ah batteries I guess then 40 minutes of my time would be spent waiting for them to charge. Don't forget if on a job you'll be stopping the job / climbing down the ladder more often to go and charge the smaller ones and no doubt getting waylaid etc. BTW what's it for? Site, home? I use my Makita for heavy DIY use and TBH really give it some - drilling multiple RSJ flaanges with 14mm hole saws etc. Enough that I could really do with a SECOND 3.)Ah battery.would you say it is better to have 2 1.3ah batteries, or 1 2.6 ah battery??