IMHO Voyager looks more dated then B5. Why? Because Trek is about the technology. Babylon 5 is about the characters, it's just by chance a SciFi show. And since the technology is not what the Series is about, the technology does not get that much attention in Trek.
About Special effects, makeup etc: A few things look terribly Dated (Example: The entering pod in the Gathering. The Psi Corps head quarters seen in Epiphanies and others. Earth Dome as seen "In the beginning" (It looked very cool in Matters of Honor - they still had different sopecial effect people back then), the makeup in the gathering) but in general they did a great job considering their budget. Makeup is a lot better then in other TV shows because they usually just had the better ideas - Realistic Ideas like the Minbari and the Narn. Star Trek (I like the show, hey, but I need to bash something down to elevate B5 /forums/images/icons/tongue.gif) seems like every alien just had new doodles on its forehead. sometimes these aliens just look so plain damned stupid (remember the guy in DS9 who had a ridge on his nose that went over his head and was connected to his chin? What poing does this ridge have except making eating, talking and lots of other things hard?