Here's an off the wall solution. A friend of mine lived in an area where there were almost no power outages, even in bad storms. They've experienced maybe 4 outages in 25 years. However, if there was an outage, it might last only 30 minutes at most. In that 30 minutes, their sump would fill up and water would start flowing into the basement. The expense of a full fledged back up system wasn't that justifiable. He kept a oil drum crank handy just in case but wanted something less labor intensive. He was more concerned about the few times a hurricane might come through and, just something as an alternate course of action. We picked up a Xantex 2000 watt inverter with a 4000 watt surge capability, a marine battery and a small solar panel to keep the battery float charged. During one heavy torrential down pour, we put it to the test. We unplugged it from the power and plugged it into the inverter. It worked great for over an hour (when the rain stopped.) Just knowing he had an alternative was good enough for him. With a little more work with a relay, we could have made the system automatically switch over. The good part is, when the battery starts to run down due to long use, you just hook up jumper cables to a car or tractor and you're back in business. We also tested it on his pellet stove and it worked great. Of course this is an "un-packaged" UPS. The cost was around 175 bucks total. He has an area where he uses a hedge trimmer and needs 150 foot extension cord to get to it. He took the setup out to the location and used his hedge trimmer with it and needless to say, it worked great. I personally think running the extension cord would have been easier but I mention all the other uses as another example of the setups' capabilities where it can be applied to other emergency or short term uses as well.

Does anyone have information on these Battery backup sump pumps: Pro Series PHCC-2400 or the Watchdog Big Dog? Any pros and cons?

OK, option 1 is not really an option. I guess I would prefer option 2 as long as there is no harm in having an extra check valve in the mix.

One check valve will work with "SOME PUMPS" but definatly not when one or both are centrifugal. Think about it like this,if a centrifugal pump is transfing liquid from one container to a higher container and the power gos off. The line will spyhon the upper container back in to the lower container. In your case,while either pump is running,water will take the path of least resistance which is the non-running pump unless there is a check valve between them. Use 2 chek valves and save yourself a flooded basment.