Since most of the comments are coming from those that have experience in both pools, most of the responses have been a bit misleading. For one, on a per date basis with the end goal being to "smash" said lady, SBs are almost always MORE expensive than the typical SP on LL. And if you develop a connection and see a SB long term, there will be other associated costs like dinners, drinks, occasional gifts and the obligatory, "I'm a little short this month for XYZ, can you help Daddy?"
Yes, if you consider the social time aspect of a SB date then it would be "cheaper" as most aren't charging by the hour like a pro SP would. But seriously, why would you pay to have dinner with an SP when all you want to do is fuck? Pro SPs charge anywhere from 250 - 350 per hour with the lower end and amateurs going as low as 150 for a wham, bam, thank you in 30 mins or less. But for SBs, the going rate is between 300 - 500 per date plus dinner/drinks, etc. if you both agree to go that route. Keep in mind, there are plenty of SPs masquerading as SBs on most of these sugar dating sites. It used to be more clear cut but nowadays, the lines have been blurred.
In the end, I'd have to agree with wintersurfer, one isn't better than the other. Just different strokes for different folks. Just make sure you have plenty of paper in your wallet.