If you like the OpenACS db api better than ns_db in the first place,
then you are also going to like it better for accessing your second
database as well. The only question is whether you want to take the
trouble to back port the mult-db support to 4.6.x or not. If you're
going to have lots of code that needs to talk to your second database,
I'd do it. If you just have a couple utility procedures, then it's
probably not worth the trouble, just use ns_db for now and you can
change those couple procedures when you upgrade to 5.0, if you feel
like it.
Hm, when is OpenACS 5.0 scheduled for release anyway? I'm not sure.