Ok, I have two chips: E3 1220L v3 and E3 1240L v3
Both very low power but still noticeable different. Here are the two tasks:
A low power NAS running ZFS, just storage, no transcoding or stuff like that.
Gonna have 32GB RAM and up to a dozen rustspinners.
A personal services server for notes, small files, searx, something like pocket, maybe email…
Basically something to get further with the degoogling, the cloud at home, you get it.
So, which CPU should go into what machine?
Raw performance wise the 1240L V3 is 3.5x faster than the 1220L v3, but I suspect either are totally fine for both tasks, so I’d put the lower TDP (and raw performance) part into your storage, as that gives you a little more wiggle room to add more features to the personal services server and generally muck around.
In my experience (tested with low end Pentium vs a haswell i5 and a quick google to check its typical) there doesn’t seem to be huge benefits to bigger CPU performance in a normal home level ZFS2 array… although if you have a massive pool of disks and many clients wanting access at one this may change, so I’d be more inclined to install the 1240L if that sounds more like your use.
To be honest you could probably just put the 25w part into the NAS and also use it as the services server rather than running two boxes at all, but again for the sake of being able to muck around and crash it you may as well spin up the two if you have the hardware, even at Hamburgs higher average energy price than the states your only talking on the order of 20 Euro a year. Having said that I’d build the storage server first and test it, then decide to keep it or assemble the other way around… no point building both to then need to change when they are both LGA1150 socket parts that support ECC and the same number of memory channel\PCIe lanes.
Anything is better than a 1220 or 1225 (I have a 1225 trust me)
@SheepInACart I think you’re right and I also just remembered a NAS build from the old days, the dark ages before it was L1T. That thing was running on an Intel Avoton, basically an 8 core Atom CPU. And it had shit to do, 10 disks, 64GB RAM… So I guess I should be fine.
True.
I have a 1220L v3 in my pfsense box and it works wonderfully there. I suspect for your NAS it should be fine. 1240l v3 would be nice but they typically cost 3x as much as a 1220L.
1220L is usually 2-6x cheaper than all other e3 12xx v3 series chips.
Same here.
I already have those chips. I was just wondering where to put which one.
I came to the conclusion that if I had to fix something in a few months it is easier to power down a “just local storage” system than a server running a bunch of services. So I will use the 1240L v3 in my cloud thingy and try to get away with running the Crappy Processing Unit in my NAS.
Thanks everyone. 
So I thought about this for a while and changed plans, mainly because of the 32GB limit on the E3 12X0 v3. ZFS likes lots of RAM and I might end up stuffing the NAS with eight 10+TB drives at some point.
In the end I went kind of nuts and invested in another sandy bridge platform, specifically a Xeon E5-1230L (that was by far the cheapest L part around at 60,- bucks), a Supermicro X9SRA and 128GB regECC DDR3 in 8 DIMMs (DDR3 is still a lot cheaper). 60W TDP is a lot more than my other chips but low enough to not be a problem. Also with that CPU it should be possible to really take advantage of 10Gbit.
The personal server is also profiting from this, it will get the full 32GB memory that were planned to go in the NAS. I’m sure over time I will find ways to make use of that.