My opinion would be to take both. We never considered having more than one cat until our daughter moved back home and brought little Mika with her. Since then our lives have been enriched double-fold. Mika and Bijou love each other, play (sometimes roughly) with each other, sleep with each other and continue to show their love for us humans as much as before. They keep each other company during our days away at work.
I can't imagine ever owning a single cat again. There are some Siamese breeders in our area that won't adopt out single kittens - they'll only adopt in pairs.
I vote for getting both too! Having two kittens is awesome. When you're at work, they still have someone to cuddle up with and play with so they aren't as lonely. They tend to get into less trouble because they can play with each other instead of going where they shouldn't, destroying things, etc. It also helps them to socialize better, especially since they teach each other to play "nice" so they don't hurt each other. That means softer bites in play and no claws, or at least less claws, in play too.
I think they need to be together. I had Mitzee and her son Remy. Mitzee died from eating rubber bands...still have no idea where she got those. House mystery. Anyway, Remy turned into a horror. Did things he never did like scratching stereo speakers, pawing furniture, pooping on my throw rugs. He now has his little 1/2 brother. Within 3 days they have bonded. We call little Skye, Remy's hamster. Remy is 18 lbs . Its been wonderful to watch Remy become normal again. His bad behavior ended over night!!
As an Aby breeder I would say take both if: 1. you can afford it, 2. you have no other cats involved. Abys are wonderful cats and owning two does make a huge difference. You will neuter them both I hope to avoid dominance fights.
A little warning - Abys love to be vertically challenged (in other words, they love high places) - if you are the kind to keep fragile things in the open, don't.
If your cat(s) go missing, look up, not down to find them!
Good luck and I can guarantee that buying an Aby or 2 will be a decision you'll never regret!