I don't think you can go wrong with either unit. The PE Summit is a big stove that puts out a lot of heat. It has a strong following here, and I am yet to see negative reviews on it.
The Avalaon Olympic is another good make. This is made by Travis Industries, the parent company of Avalon, Lopi and Fireplace Extrordinare. Once again, another strong following on the Hearth forums.
Speaking of Travis Industires, you might consider the Lopi Freedom. It is essentially the same exact stove as the Avalon Olympic, just a little different asthetics. Personally, I like the look of the Lopi Freedom a bit better, but the features and specs are almost identical (both have the bypass damper, 12 hour burn times (advertised), ~74,000 BTU's, etc.). The Avalon has a slightly larger firebox (3.1 vs 2.9), as the Freedom's firebox is tapered. If you have a smaller fireplace and space is tight, you might consider the Freedom if the measurements are a concern. If not, it's almost always better to get the biggest firebox possible, thus the edge goes to the Avalon. Different strokes for different folks, as they say.
In the 3+ CF firebox, you might also take a look at the Osburn 2400 and Lennox Canyon C310. These two stoves, along with the Lopi Freedom and PE Summit were my 4 leading contenders. I had placed a deposit on the Freedom, then cancelled it... almost placed a deposit on the Osburn 2400.... backed out last minute as I was still undecided... and FINALLY (yesterday) settled on the Lennox C310. It's scheduled to be installed next Saturday, and I am very excited!
I really don't think you can go wrong with any of these units. They all offer large fireboxes, plenty of mass and heat output, and long potential burn times. For me, the Lennox won out due to dealer location and availability. Also, the Lennox was the most expensive stove of the bunch list-price wise, but the dealer ended up offering a quote less than that of the local Lopi and Osburn dealer! And my comfort level with the Lennox dealer was the highest, so I ended up placing the deposit yesterday. Everyone's tastes and needs are different, but it's nice knowing you can't really make a "bad" decision.
On paper, these 5 stoves look very similar. Here is a quick summary for reference:
PE Summit: 465 lbs, 20" max log size, 6" flue, 99,000 BTU, 3.0 CF firebox, 80.4% efficiency, 10 hour max burn time
Osburn 2400: 545 lbs, 21" max log size, 6" flue, 100,000 BTU, 3.2 CF firebox, 78% efficiency, 10 hour max burn time
Lopi Freedom: 455 lbs, 24" max log size, 6" flue, 73,300 BTU, 2.9 CF firebox, 75% efficiency, 12 hour max burn time
Avalon Olympic: 470 lbs, 24" max log size, 6" flue, 74,300 BTU's, 3.1 CF firebox, 75% efficiency, 12 hour max burn time
Lennox Canyon C310: 547 lbs, 22.5" max log size, 8" flue, 84,500 BTU's, 3.1 CF firebox, 78% efficiency, 12 hour max burn time
Note that advertised BTU's, burn times, and efficiencies are sketchy at best (trying to duplicate these results consistently in "real world application" is not realistic).
In the end, much of your decision will likely come down to personal preference and supporting dealer location/availability, as was the case for me. Good luck in your decision! And be sure to take advantage of the $300 2013 tax credit!