@Justin Lewis
Being a Realtor I do have access to more platforms than the average Joe. With that being said, as long has you are getting your comps from a reliable source and you know how to adjust for the differences you should be ok. This is literally what we do each and every day so agent are more refined at it and it can take them half as much time if they know where and what to look for.
@Justin Lewis
Computer will not give comps, only guess. You have to go inside each house to get real comp. there are too many things that computer can not grab.
If you invest money based on computer data, that is a big mistake.
There are so many analytic tools available now to understand values and trend analysis. I still use Trulia, Realtor.com and occasionally Zillow esp for their new rental trends. If you really want to go deep a BPO Broker Price Opinion can be done complete with exterior pictures for around $150. I can refer one or more if needed.