I have both (520 and 330) and I can't tell the difference in day to day use (microsoft office, browsing, games).
The 330 differs from the SandForce based Intel SSD 520 in a couple of key areas. The 330 uses lower p/e count NAND (still Intel 25nm MLC) compared to the 520, reducing Intel's rated lifespan from 5 years of 20GB of writes per day to 3 years under the same workload. Intel's ratings have historically been conservative, so I'd expect that the 330 would last much longer than 3 years for the vast majority of workloads - particularly based on previous calculations on the topic. With a 3 year usable lifespan rating however, Intel dropped the limited warranty on the 330 to 3 years as well.