First off Pandian isn't officially supported, it has too large of a footprint to fit on the 512MBs of internal NAND storage, it only can be booted from SD card. Pandian Mark III is the latest and hasn't been updated in a while. It won't have some of fixes in the latest kernel builds, nor driver updates and what not. Secondly 3D accelerated games won't work with Pandian as the GPU driver only has soft-float drivers and pandian is compiled for hard-float. The benefit however is you are connected to official Debian repositories with all the current packages and what not, since you need to run off an SD card your only limit is the size of your SD card. This may not be a bad option if you only care about coding and what not.
Angstrom's benefits is that it's optimized for the Pandora hardware, the OS fits on the internal NAND storage leaving both SD cards for application use. I can't tell how familiar you are with the Pandora and the PND system which was designed for use with removable media like SD cards and thumb drives, so I'll explain it anyway. A PND is a package that allows you to just copy it to an SD card and it will appear in the start menu, desktop or both depending on which directory you copy the PND file to. Things like settings and user data is stored on the SD card as well in an appdata directory that is automatically generated for each application. You can hot swap SD cards and what not without disruption or breaking dependencies and such. It's up to the community here to generate these PND files, luckily we have a ton of talented people here. The official repository is on this website:
http://repo.openpandora.org/ One of the first things I recommend is installing PNDManager and then you won't have to use the webpage to download programs like the Java runtime installer PND, Libreoffice and what not. For programming there is a couple options, I recommend the Code::Blocks PND, it's a pretty large download, I don't use the actual Code:Blocks program itself, but it does have a CLI option that gives you a terminal with all the major programming languages, fairly updated GCC version and updated development libraries and what not.
Angstrom is a bit odd to deal with if you are used to desktop flavors of Linux, but to me it's the best mix for usability... Slackware is another option that you can boot from an SD, it has working 3D acceleration the PND system is enabled and works with most PNDs...
I'll let others answer and I'm a tad tired right now.