Plus base pads or Mag Extensions will add 20-30 extra likes on your edc pocket dump picture for the gram. But seriously there are some actual practical advantages behind adding a magazine extension. Yes, you will definitely be able to cram three to five more rounds in your magazine depending on what brand base pad you go with.
Mag extensions give me more area to contact on the mag when reloading. The extension is increasing the overall length of the mag and a lot of times mag extensions will also have texture or stippling. When your hands are wet or cold you can really reap the benefits of a little more real estate to work with.
Getting the empty mag out of your gun is half the battle when reloading. I prefer to use Glocks and it can be a problem for the mags to fall free with the polymer on polymer contact between the mag and the gun. The additional weight to the bottom of the magazine from a plus base pad is welcomed you need that mag to drop free.
I would not recommend putting mag extensions on a all your mags because I do not think the cost is justified to do that. Plus base pads can range anywhere from $30-$40 and you can easily buy another magazine for that price sometimes 2 magazines. I would suggest adding two or three mag extensions to your regular line up of magazines. Of course the additional ammo will be welcomed but you may also find reloading in general a little more efficient.