First off, I'll say that you could buy a storage array from almost any reputable vendor/reseller and get a good result provided you have given them an accurate description of your requirements. The problems tend to come as your requirements change over time.
For most of us, our abilty to predict the future is fairly limited, so we manage this uncertainty by overengineering our solutions by building in a fair amount of headroom, the second problem is that business requirements have a nasty habit of changing in ways we cant easily predict (e.g. most people didnt expect their IT budgets to get frozen last year)
If you never expect to outgrow the capabilities of the box, and that you wont need to reclaim any wasted space via thin provisioning and deduplication, or get tight integration with Vmware, or Xen, or Hyper-V then an MSA or something even dumber and cheaper may do the trick for you.
Remember with the MSA, if you outgrow it, you have to move to an EVA or something else, with a 2040 if you outgrow it, simply upgrade the controller hardware to a 3140 and you've turbocharged your storage environment, but everything else remains the same. I'ts this kind of investment protection that saves you lots of money in the long run. Also with FAS, if you undersize your solution, you can easily and nondisruptively add more spindles (and hence more performance and more capaicty). It's this kind of elasticity that means you dont have to oversize the solution in the first place. Just in time purchasing of disk can save you thousands over the lifetime of your equipment.
On the performance front, In general HP SAN products get pretty average IOPS / spindle (lots of reasons for this), I'm pretty confident that you'll get at least 20% more IOPS out of a 2040 for the same number/type of disks. In addition their snapshots are all based on copy on write which means terrible performance under heavy write loads, and I've never met a happy customer running HP replication software.
Finally, the price discrepancy you mention is pretty high, I've seen this before, generally when someone compares a bare bones HP or Dell array with a NetApp array plus all the software features including snapmirror, snapvault, flexclone, snapmanagers etc etc. If you're going to do an "apples for apples" comparison, make sure you're comparing the same things, get a price for just the bare bones 2040 without snapshot capacity reserves (chances are that the EVA pricing doesnt include capacity for snapshots) or any additional software. I suspect you'll find the pricing for the 2040 will be about the same or even lower.