I have both scopes and I can ensure you, you can't go wrong on either.
If you'd ever need 4 channels, you can not upgrade any of them, so that would be your most important decision upfront.
The pros and cons on both are mere details, there is no showstopper or killer feature on anyone - unless of course you'd be looking for one particular must-have, e.g. the large memory of the Rigol or the Wavegen on the Agilent. But then you wouldn't seek advice anymore?
If I had to give up one of them, I couldn't decide...so, I'm glad I don't have to
Techspecs have been discussed already and you can look em all up, so I'll just add my personal little(!) pros and cons:
Rigol:
+Large memory
+Better user interface (more softbuttons=less menu fiddling)
+Tons of features, even in the basic version (e.g. the statistic plots are great, i think the Agilent doesnt have that at all?)
+Probes seem better build quality than the Agilents
+Analog frontend less noisy
-Fan is more noisy though
-Button illumination is rather dim
-Whole front panel looks a tad too chinese...like in "cheap and colorfull"
Agilent:
+Wavegen comes in handy at times
+Love the probe compartment
+Fan is rather on the quite side
+Overall built quality, look and feel, the better button illumination...it just makes it more enjoyable to work with.
-The probes though, they feel somewhat cheap and clunky (the "hook" looks like a bent paperclip)
++Professional support: Had to do some SCPI programming for a customer project. All the drivers, the documentation, just everything you might need is right there on the website. Email questions get answered right away, they even gave me phone numbers to call in case of any problems. Also the distributor always lends a unit or has replacements available, should yours have to go for repair or whatever.
With my Rigol, I am not so sure about that. For basement use only though, I wouldnt care at all.
They both have this analog-like waveform display (not just pixels in a single line, but gradients that cover the whole range of the signal) which to me is one of the most important features and they both seem to be doing a pretty good job on that (my analog scope is just collecting dust now). Neither of them feels slow or awkward to use, they are very responsive and I never had any crashes or hangs (except with the Agilent when it didnt like some SCPI stuff I sent to it).
To sum it up, the Rigol sure offers more bang for the buck when you just tick off a list of features in the unit. On the other hand the whole Agilent infrastructure is absolutley priceless should you ever need it.
Whichever you pick, you'll love it, no doubt