It can work both ways
Eq before effects has more control over your base bass tone
Eq after effects can help correct overall freq problems/enhancements
+1 on this.
Other people's experience and opinion might be different.
Here's mine, based on what I see what's important in effects *inputs* and *outputs*.
- effects like dirt (OD, distortion, fuzz), octaves, envelope filters, synths react most strongly to the *level* of the signal coming into them, and much less so to the tone of signal;
- effects outputs almost always (excluding delays/reverbs) affect the *tone* of your signal.
Now: where would you put your EQ?
My opinion: effects don't really care much what is the tone color of the signal that you feed them. So EQ in front of them would be pretty useless - you EQ your signal one way, and what comes out sounds completely different. Effects do affect tone *a lot*, and often in a way that you don't have direct control over. But if you have your EQ after them - you have a good chance to fix what you don't like about the overall result.
One exception to this - might be specific to EBS Octabass (that I use) - octavers. Mine likes a lot of low freq in its input - it makes tracking much better than when I compress the signal before it (actually, I found that compression makes it worse for EBS, despite their own advice to do that). I deal with this by boosting lows on my bass (active) when I use octaver.