I personally love the original cards. They're fairly easy to bring back as well. You just use a hair dryer around the edges to heat up the glue, and carefully use an x-acto knife to pry it apart. Solder out the old battery and put in a new one.
Console5 sells replacement batteries which makes it much easier.
<p><em>High-quality</em> Panasonic CR2016 3V Lithium Battery <strong>with solder tabs</strong>.</p> <p>These batteries are authentic, name brand replacements for Neo Geo AES / MVS memory cards. <em>Beware of similar-looking generics!</em></p> <p s
console5.com
And you can bring them back within 20 mins. I've picked both mine up dirt cheap listed as "not working" and now I have 4 of them. Personally I just like the look of them. But if you just want to save high scores and use a multi-cart I can see going the NeoSaveMasta route as a better option.