I've programmed with Debian, Ubuntu, and Slackware, and Slackware wins hands down. Ubuntu mirrors don't always have current packages, so if you are, for example, working with a Lamp stack, you are limited to the package versions the mirror maintainers think you need instead of what you want. Unless you know how to download/compile/configure Apache and mysql and PHP yourself, and most people that use Ubuntu don't know how to do this.
In a way it depends on your skill level. If you are a beginner, you might want to stick with Ubuntu. If you know what you are doing and you want more control over your development environment, go with Slackware. I use Slackware with the most current versions of PHP/Mysql/Apache.
FWIW, updating slackware is a breeze IF you know what you are doing. Again, for the beginner, Ubuntu might be a better choice.
I've been working with computers for 30 years. I despise Windows, and I use Slackware because it is a more pure form of Linux. It doesn't have any branded garbage, it lets you do anything you want without getting in your way. I prefer it over Ubuntu or even Debian.
In then end it comes down to skill level and preferences. I have a high skill level and like to control things, so I use Slackware. Those that don't have a high skill level might prefer Ubuntu.