No problems 
If you go and have a play with HKJ’s excellent 18650 comparometer and compare an unprotected Panasonic 18650B to the various protected versions of the cell, you’ll notice quite a large performance variance across differently branded cells at a 5A discharge rate. For example:
The Keeppower ones are very good as they use a decent protection circuit and lots of other sellers (www.intl-outdoor.com for example) carry re-branded versions of these same cells. But whilst they are indeed decent, they are not the best if you’re trying to match the discharge curve of an unprotected 18650B cell as closely as possible. What we want to see is something more like this:
I’ve had no personal experience with those particular Efest cells but they clearly demonstrate the existence of extremely low resistance protection circuits. I bet it has something to do with the differences you can see in the following tear down that RMM did here: Evva vs. Keeppower NCR18650B Protection PCB Visual Comparison
Notice that the Keeppower cells use a protection circuit that utilizes only two mosfets (which is undoubtedly already more than most), but that there are other protection circuits available that utilize 3.
The following seller, whom I’ve bought all my own 18650s from, is selling cells assembled by Keeppower but which additionally include the lowest resistance 3 mosfet protection circuits he could source: http://www.ebay.com.au/itm/2x-BLAZAR-PROTECTED-Panasonic-NCR-18650-B-3400mAh-Lithium-Li-ion-Battery-NIPPLE-/281004345565
It doesn’t look like our good friend HKJ has tested any of these yet but I bet they’d fare very well in a head to head comparison with unprotected cells at 5A.