I've got the Boss DD-20. And i love it. I was in your position not long ago, but i've fallen in love with my 20. It's really great.
Sounds great, the analog and tape delays are pretty convincing, but for the price, i'm not too fussed. If anything, you might need to get a seperate foot switch to tap the tempo, but apart from that, i love it.
I haven't ever tried a DL-4, so I should maybe not post but I can't resist.
I have the DD-20 (with a separate tap tempo switch), and I love every inch of it! It is way nice, lotsa great flavors to be found in there. The digital display adds the nice finishing touch to your pedalboard too. :13:
My only gripe would be the layout of the presets -- I think the DL-4 excels at this. And the DL-4 seems to have some great sonic possibilities in it, maybe far more than it is for the DD-20, I don't know.