Soundwise
OK, but why? Why would you use tape/console emu at all?
For some of us - probably not many, but some for certain - we create music exclusively with software synths, everything in the box. I do this, and on top of that, I almost religiously avoid using sampled real-world instruments unless those samples originated on a synth to begin with. Why - what does it matter? I'm doing this primarily for my own gratification, and when you're following your bliss, you get to make up your own rules.

So, to answer your question, I use a tape emu (Magnetic II, in my case) because the vintage fairly dust it adds makes the final mix sound better. And as we all know, if it sounds good ...
If I were mixing conventional tracks in some popular genre, I'm pretty sure I'd be taking a different approach. But for software synths, a bit of vintage sheen tops things off nicely.