I have installed and run the Edelbrock Pro Flo system on a few motors over the past 10 years and can say that it performs very well. On my current motor I run the F.A.S.T. system, which in many areas is similar to the Holley 950. What you will find on the Holley system is a lot more open access to tuning parameters versus the Edelbrock system. This can be an advantage on a motor that is quite radical or falls quite a bit outside of the preprogrammed base chips available from Edelbrock. This is not to say you can't get as good a tuneup on the Edelbrock though as there are workarounds to it. If you have a fairly mild combination, around 400-475, both systems will tune in very similar.
An advantage to the Edelbrock is not having to purchase/use a laptop for tuning. All in cost is also lower. A disadvantage though is the sytem does not have a lot of growth potential, nor do you have the ability to run closed loop fueling. Nitrous or other power adders are also not supported well, if at all with the Edelbrock system.
Edelbrock has a new fuel injection system on the market now that is similar in design to the Holley. This new system is in fact much more advanced and extremely nice. It is very easy to setup, has self tuning features and appear very robust in design. It would be worth considering if your looking at EFI.
The Accel Gen 7 system is also worth looking at, although setup and tuning can be challenging for the first timer.
As a first timer I would suggest buying a system from a vendor that has a proven track record of customer support.