Mac Pro 5.1 6 core vs. 2013 iMac

Question

This is probably an odd question, I know.
I'm a medical student currently working on a 2010 Macbook Air. I have ~$1800 to spend on a machine that I want to last me for another 4 years at least.
No, I don't do any video editing or anything like that. My primary usage is research with multitasking (i.e. I want a couple dozen browser tabs open, MS Word, Powerpoint, and Endnote open without noticing much lag as I do currently).
I have a local seller with a 2010 Mac Pro 6 core 3.33 + 16GB ram for $1800.
My other option is a 27" iMac i5.
I'll put an SSD into both of them.
The raw power of the Mac Pro attracts me to it, which makes me think it will last me longer despite being a few years old already. Also, I don't want the 21.5" iMac because I need a large screen so that I can have Word and a browser open side by side, so the i7 model is out.

Answer 1

Hey, dudes, i don't want to start any trouble.  Your machines are very nice.
But you're missing the point.  Most software does not take advantage of multiple cores, or can only do so in a limited fashion.  Geekbench single-core scores are not analogous to a one-cylinder engine test.  The difference in the test is that the multi-core version is written specifically to use as many cores as possible, and include special CPU instructions that do parallel processing.  The CPU is not "limited" to using a single core, and if you monitor your machine, you'll see it doesn't just use one core.  The benchmark measures performance WITH SOFTWARE THAT CAN/DOES TAKE ADVANTAGE OF MULTIPLE CORES, vs SOFTWARE THAT CAN'T/DOESN'T.  Look for explanations at, say,  http://macperformanceguide.com/ or http://www.macworld.com/article/1162105/macworlds_new_speedmark_7_benchmark_suit e.html .  The vast majority of software does not make good use of multiple cores, and will benefit more from higher clock speeds (and Turbo-Boost) than from more cores.
The vast majority of software does not take good advantage of multiple cores, and nothing the OP listed does.  Even with multi-core specific software like Photoshop, etc., it may be able to take great advantage of 4 cores but not much beyond that... so even pro video oriented reviews talk about (in comparing Mac Pros to each other) the 6-core as the "sweet spot", because its higher clock frequency trumps the number of cores (6-core at 3.33 vs 12-core at 2.93 GHz, etc).  Look at the inverse ratio between "ordinary task" performance and "core-friendly" task speed nicely laid out in the CPU discussion at http://macperformanceguide.com/ .  Look at barefeats.com comparisons of iMacs vs. Mac Pros over the last few years.
So, as a rule, a faster 4-core machine will outperform a slower 6, 8, or 12-core machine of the same processor architecture on most tasks.  The high core counts are there for very specific applications where the parallelism vs. clock-speed tradeoff is carefully engineered to take advantage of more cores.  This is actually a very hard (often impossible) thing to do; taking advantage of higher levels of parallelism has been a Holy Grail of Computer Science for decades with only small, specific improvements in limited tasks.  Single-core vs dual-core or quad-core performance often makes a significant difference because there is some "naive parallelism" in the OS overhead, the running of different programs simultaneously, etc., but testing has shown that beyond4 cores there is not much benefit for such "naive parallelism".
So, for our OPs intended use, the iMac will likely be faster and more responsive.  If he had said we was going to be doing a lot of complex rendering or video editing, I would certainly suggest the mac pro instead.