If it is any guideline with similar use, plus some iPhoto editing over the past couple of years…...
My base model early 2009 Mini is still going strong after nearly six years of being on mostly 24/7 (sleep mode when not in use). It came with 1 GB of RAM, to which I added 4 GB when I upgraded to OS X 10.8 (Mountain Lion) a couple of years ago. I expect it to be good for a few more years yet, though suspect Mavericks with be the last OS X to support it.
The base model 2014 Mini will not be a speed demon. It's underwhelming specs and minimal increase in tested performance over its predecessor have drawn scathing remarks from knockers on forums. There are those who will advise you to go for higher spec, more RAM and SSD, and then moan about how much extra it all costs.
However many users and reviewers have found the base model 2014 Mini adequate for basic use, and by far the cheapest way to get into OS X.
Personally, now that photography has come into the picture for me, I would be inclined to go for the mid-range model, possibly with Fusion Drive if I was replacing what I have now. Otherwise I would probably be happy with the base model. In the end it all depends on your use and expectations.
Can't comment on how the 2014 Mini would compare with the Dell described, but reckon it would have to show some improvement. I do occasionally use other computers and OS, but have only ever owned, and mostly use Macs. Getting used to OS X may take a little time, but once done you should reap the benefits.
