I have configured and installed hundreds of Sonicwall devices into customer locations. A business class device such as this, compared to a consumer class device like the Netgear, will have greater throughput. On a multilevel house, you may have to use multiple access points to have solid wireless connections on all levels, however a Sonicwall with wireless built in has greater signal strength than consumer wireless. Another plus on a business class device is that it usually has better security and controls. The downside is you would need someone versed in whatever business class device you buy to configure it properly for your VOIP and other networking needs.
Since most consumers don't do much more than unbox, plug it and start using their devices - rarely does the default wireless channel get changed - thus you and all your neighbors may be trying to use the same wireless channel.