well, i've had experience with coralife skimmers and know them to be of much less quality than their competitors. i don't think i've seen anyone who has knowledge of skimmers mention that these perform well.
i have also seen the eshoppes skimmers running at MACNA and took a good look at the different models and i was not impressed.
that psk-100 is way underpowered for your tank. i would probably consider something of that size for maybe a 40 gallon, but again, i'd probably want something better quality anyway.
a protein skimmer is either going to be a major component in the filtration of your system, or just a giant aerator. i believe the 2 you chose aren't going to do a whole lot other than aerate the water.
also, it's a good practice to look for a skimmer that is rated for 1.5-2x your system volume. these manufacturers tend to rate these skimmers for more than they can handle IMO, and some companies rate them for MUCH more than they can handle.
the only trouble i've heard about the space saver cone is that when you need to do maintenance to the pump, you have to remove the entire skimmer from the sump. that might be a P.I.T.A. for some.