As noted before, the hitachi will be hard pressed to go over 100MB/s in practical terms.
All that "SATA3" labeling in HDDs is just affirming compatibility with the technology. The disks are as fast/slow as before.
There are very few SSDs in the affordable range that can fully use the SATA3 6gig bandwidth.
A cheap SSD drive may have a mediocre sequential performance (not very different from an HDD), but still will be a whole lot faster on seeks and random reads.
Sequential is for copying large files etc, but that you will hit a bottleneck somewhere else long before anyway.
The responsiveness and "perceived quickness" of desktop OS usage is mainly due to the random-read performance.
Also, low end SSDs tend to have a non-scaling write performance (they don't write as fast as they read, the speed changes a lot and so on), but in usual notebook that is not a big issue.
Go for the SSD.
Beware, it will feel great at first, but you will get used to it just as fast :)
2"I have Hitachi HTS727550A9E364 HDD, which according to this site has a 300 MBps transfer", not quite... The drive's "Interface transfer rate" (SATA2) can support 300 MBps (MegaBYTES), but the drive itself (See: "Media transfer rate") can only do 1247 Mbps (MegaBITS). The SSD will be magnitudes faster, even at SATA2 interface speeds. – Ƭᴇcʜιᴇ007 – 2014-07-04T17:05:24.820
@techie007 Thanks for clarification! – pmichna – 2014-07-04T17:07:37.633
Related/Possible duplicate: Can I install a SATA 6 Gb/s SSD on a laptop that came with a SATA 1.5 Gb/s hard drive?
– Ƭᴇcʜιᴇ007 – 2014-07-04T17:12:23.567@techie007 generally yes – Aboba – 2014-07-04T17:15:05.120