Query String vs Stored Procedure preformance (500 points)

I am trying to figure out the impact of passing a long querystring from my webpage to SQL Server, I know that it will slow things down a bit versus using a SQL Stored Procedure, but I need to do it this way.   .  It seems to work fine when I pass it from my web page to sql, I don't notice any slow down, but my concern is if I have alot of members running this query.  So if anyone has any Idea on the bandwidth usage and any other preformance issue that may arise with the web server or the Database Server.  It would be helpful.  

***This is the code***

sSQL ="SELECT M.MemberID , Z.Distance,M.Region,M.Smoker,M.Preference,M.Age,M.FAge, M.TAge,Distance FROM Member  M,(SELECT z.ZIPCode, dbo.DistanceAssistant(z.Latitude,z.Longitude,r.Latitude,r.Longitude) as Distance FROM ZIPCodes z, RadiusAssistant(53151,40) r  WHERE z.Latitude <= r.MaxLat AND z.Latitude >= r.MinLat AND z.Longitude <= r.MaxLong AND z.Longitude >= r.MinLong AND CityType = 'D' AND ZIPCodeType <> 'M' AND dbo.DistanceAssistant(z.Latitude,z.Longitude,r.Latitude,r.Longitude) <= 40)as Z WHERE M.PostalCode = Z.Zipcode  Order by Z.Distance"


Thanks
mcsdguyian