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As I said above, they should technically clock slightly better.
A 100MHz bump over the 2500K is no indication that they should clock faster.
If Intel released a 25xxK version at, say, a comfortable 3.8GHz would that be any indication it would clock better than a 2500K?
The 2550k would be expected to go about 100mhz higher, as they are chips that are clocked 100mhz higher at stock, so you'd expect intel to cherry pick the higher potential chips, and then disable the GPU.
Obviously this would not hold true in all situations.
If 3.8Ghz was stable with the same stock voltage of the 2500k then yes, it likely would be a better clocker.
Nope there isn't, and as stated, the 2550k is simply the 2500k with no onboard iGPU.
No it wouldn't.
Most (I'm tempted to say virtually all) 2500Ks will run 3.8Ghz without increasing the voltage.
It's no indication that one is a better clocker than the other.