It depends on the battery used. Some have memory problems, causing a shortened life..

which ones are better?

I've responded to this post already in a couple different ways. Now, when Focused more on it, I realize I left out some information which might be helpful.

So, regarding charging your rechargeable toy anywhere in the world. For this I'm going to use a cell phone as an example. Like the Apple Iphone, all cell phones for the most part are used world wide and designed alike, exactly alike, and thus are the same everywhere. It does not make sense to manufacture a phone for each country. A few years back, manufacturer's were supplying a separate charger for each specific region/country of the world based upon voltage and cycles. Back then, I can remember burning up my Nokia phone in Australia. This was because my charger was for the USA market which is 120 volts. However, the Australia market is 240 volt. Besides the voltage differences, each region or country uses different prong styles and configurations. So, what is different now. The manufacturers realized if they produced just one charger for the phone it would greatly reduce the cost and complexity. What they came up with was the "Smart" charger. It reads the voltage of the country/region and automatically supports what is required. The only difference is the prong configuration. So, now if your traveling abroad, you only need carry simple inexpensive prong attachments, and not be worried about voltage differences.

Sex toys are like cell phones. They are the same, and are sold all over the world. They have also employed or use the same "Smart" chargers as cell phones, shavers, etc. Just have the correct prongs, and your good to go.