As was you went from 100 MB/s on the 160GB drive with IOPS to spare/good caching to 300 MB/s or so on the 480GB drive* meaning that 480GB drive is still way slower than the drives we are discussing today.
I don't know where did you pick your figures, but whether the X25-M did those 100MB/s (so sequential write, random write was much lower, around 35MB/S at best), the Seagate do around 440MB/s (260MB/S at random write), while contemporary top end competitors like the 512Gb Samsung 840 Pro do around 490MB/s (290MB/S random: so within an about 10% margin): definitely you're plainly wrong. If you mind, you may also easily compare that newest Samsung 850 Pro write performances to the Seagate ones on that link
(all the above data come from the relevant Anandtech reviews, anyway).
Well, in my experience a write speed bump around 5x (actually around 4,4x, sir, but 7,4x per random write) doesn't mean at all what you are saying.
Given that, any other comment is useless, as you just don't read (or you're not able to understand) other people points (Abula's one, mine).