Ultimately it depends on the user. Those with less knowledge of how to configure linux or with less time to do it should probably look at a mac. However if you have the time and know-how Linux on a Dell will be cheaper and possibly faster performance-wise.
Well, I've been using both linux and Mac for 15 years or so, and I'd found that Macs are often even more frustrating than linux (or other unixoid systems). Thus, when my earlier Macbook Pro was dying, I got a new one with the fancy new "Retina" display. It supposedly had twice the resolution (4x the pixels) as my older Macbook, but it was configured to mimic a tiny screen (or one with giant pixels ;-). It took me several months of googling, tweaking, swearing, etc. to stumble across useful info for reconfiguring it so I can now get 6 usable Terminal windows on the screen, though with slightly fewer rows and columns than the old one gave. I'm sure it can do better, but I've become resigned to the idea that this is probably the best it can do with its marvelous hi-res display. Much of the frustration, of course, is that questions on Mac forums tend to get oh-so-friendly answers that might be summarized as "Don't worry your pretty little head about it; It Just Works." You do get a bit of this from the linux crowd, but there are also folks who like to show off their knowledge to noobs, so if you act like a noob, they give you useful information, and further details if you don't understand something.
The main frustration with linux systems is that it has been difficult to get them with hi-res displays. I've read a number of explanations of why this is. My pocket "smart phone" has as many pixels as the big screen on my home linux box; we should be able to get laptops with about the same resolution and thus many more pixels. OTOH, the linux laptops I've used have come out of the box with the software using the the screen's full resolution, so if you have good eyes, you don't waste time hunting down instructions on how to turn off the "accessibility" stuff.
YMMV, of course; different people have different kinds of knowledge and interests. Marketing aside, there never has been any such thing as a "general purpose computer".