Providence's PEC-2 is a slightly less expensive alternative to Boss' ES-8. Featuring the same number of loops, the Providence has 5 loops wired in series with the other 3 loops completely separate. This means that you can easily split the pedals that you prefer running in the front of your amp with the ones sent through your amp's effects loop.
For example, you would conventionally place your overdrive, distortion, fuzz and compressor stompboxes in front of your amp for the best tonal results. Therefore, plugging them into the PEC-2's 5 series loops would be the best solution. That means that the 3 separate loops can be saved for your reverb, delay and modulation effects. This makes the PEC-2 somewhat more logical to setup, whereas an ES-8 or ES-5 will need to be wired in a more technical fashion in order to let effects run through both sides of your amplifier.
The PEC-2 also has versatile buffered and non-buffered inputs. So if you're running a long length of cable into and out of the switcher, the high-quality buffer will restore your signal's presence. But on the other hand, some fuzz units react badly to buffers that are placed before them in the signal chain. They are very temperamental beasts, and buffers can make them sound anaemic and weak. So if you are using a fuzz pedal, it would be best to plug into the non-buffered input so that it doesn't affect your fuzz's sound. However, if you still want the perks offered by a buffer, you should buy a dedicated buffer pedal. That way, you can place your fuzz in loop 1 with the buffer pedal placed directly after it in the second loop.