This is a great question! Generally, hardwiring your Slingbox to a router with an ethernet cable will give you the best results. However, wi-fi can give you just as good quality depending on your connection. Here is an article that gives some more information on your current situation. Troubleshooting choppy video in Watch on Slingbox.com I hope this helps!
Sling Media Forum Moderation Team
Ethernet is the connection of choice. Video is very data intensive and does not respond well to any bumps in network conditions, which happens more frequently with wifi.
If the option is availabe, forget wifi and go with ethernet. If ethernet is impossible, I would recommend buying a dedicated wifi router that would only be used by Slingbox, and keep all other traffic on the other network. They aren't too expensive, $30 for a cheap one. It may be that you already have an extra wifi network: for example, I have a firewall with one and my cable modem has another.