It is relatively easily faster. Not by a huge margin but not hard on a decent range of software.
Apple is likely to use the something like the E5 1600 v2 offerings. The current E5 1620 clocks in at 3.6 and turbos up to 3.8.
http://ark.intel.com/products/64621...-E5-1620-10M-Cache-3_60-GHz-0_0-GTs-Intel-QPI
It has twice as much memory I/O bandwidth. It probably has about twice as much L3 cache. Later in the year the Core i7 47xx ("Haswell") that the iMac will get will have a somewhat better fused 256 math ops pipeline but that won't work be optimized on most current software.
The Mac Pro's drive will be significantly faster than any Fusion drive. ( the capacity won't get matched but "out of the box" performance isn't going to be matched.)
It is very likey the that new E5 1620 v2 that the upcoming Mac Pro will use will bump that up to 3.7-3.9 GHz. ( It is technically not a "Ivy BRidge E" but uses the same base chip die with different features flipped on/off
http://www.cpu-world.com/news_2013/...ge-E_extreme_CPUs_to_launch_in_September.html The i7 4820K is basically the equivalent of the 1620 right down the price Intel charges. )
So even if the upcoming bump of the Core i7 that the new iMac rises to the current E5 1620 levels it will still behind a bit on base clock ( which will help neutralize any incremental micro-architecture advantage. )
The primary reason the iMac can outclass the current entry Mac Pro is because Intel crippled the entry level offering over two tick-tock cycles ago. They never did a Westmere update of the entry level product. The entry level , 4 core , offering has been stuck on 2009 era architecture because Intel never updated it. If Intel doesn't make it, Apple can't sell it.
From the perspective of the just only the entry level model it was more than a little crazy that Apple did nothing in 2012 (and till now) about picking up the solution/upgrade that Intel finally shipped in 2012. I realize that entry model isn't the whole line up and there were bigger issues involved. But Intel fixed the root cause of the problem of the iMac-Mac Pro gap last year.
there is a good chance there won't be any GPU upgrades and that budget will get swapped for the TB external "expansion" that will be paid for in new system.
