ohnart,Yes at least in my opinion they are, but I think if you ask other forum members here, they will tell you the same, that they are. If you want more extended play time, up to 2 hrs, slightly more with Pleos depending on things like temperature, if clothes are on, age of Pleo perhaps, etc, then even longer.
Of course there is nothing wrong with the green original batteries, if you have more than one, you can just charge another one and wait and then have two which will probably give you up to 3 hrs total play time, maybe slightly longer, One definite advantage of the egg chargers and batteries is SHORTER CHARGING TIME, 3 hrs not 4, so you can play quicker, What I like to do is use the green original one while the other one is charging or already has and when the green one is done, Pleo ready to sleep, pop out the green and put in the white and continue playing and then charge the green, Just gives you more options and more playtime, Great for those day when you want to take Pleo out and socialize with the public, Nothing worse than a tired worn out Pleo just when people are getting interested, and Pleo is ready to go to sleep.
If you don't want to spend more money on the white battery and charger, than a green back up battery is a good idea, but you still have to use the original charger that came with your pleo, Also the white batteries only work with the White EGG chargers they come with, they are not interchangeable with the green batteries. I would ask more people on the forum here to help give you an idea of what they prefer, pros cons, etc. also just for your own information, I do sell the green ones already and all my Pleo Batteries come with a Free Bonus item ! Good luck with whatever battery you decide to get or use. Pleos are fun whether they use green, white or both!

RedwoodsMama and MS. Nova and Friend