The same information hosmY has said is the same for both of the VPS above.
Let me be a little more in-depth if possible. The difference between both servers are that their configurations of hardware are either more powerful or less depending on what they have. The NL server has less CPU power however the disks themselves are probably the most important thing they have. The disks themselves are fast and are able to keep up the speed for very long constant times.
A regular SATA II 7200RPM drive is considered "fast". However, that "fast" can be for 10 seconds...or a very long time. Depending on what your doing with that drive. What applications you are running. For one person that is using it, it can be fast. For others it may be the opposite. Just a hard drive alone has a certain "limit" that it can go to and usually a hard drive alone cannot be stressed out by multiple people at the same time. Which is why many people go for RAID0 or 5 etc (especially here). RAID0 gives it that "boost" however there is also downsides that many people do not account that for. RAID0 in my opinion and probably others are "dangerous" and should be used at "your" own risk. The reason I say "yours" is if your server, home pc, VPS is just "yours" alone and no one elses. Also meaning your the only one sharing that hard drive. Because once one hard drive fails on you, everything else does as well. The data is gone...finito!. There is ways to recover but is time consuming, expensive and a headache. So I would watch out for RAID0. Unless your doing something to keep that data alive. Like taking snapshots daily?
RAID10 for example what I offer. Is RAID1 (duplicate data = redudancy) and RAID0 (speed) ..however in this case you already have data being backed up TWICE once your downloading/uploading automatically. This is also done by a hardware raid. Not a software raid. Difference? Software RAID which most providers (here have, in Wj) is that. They get the speed but they sacrifice CPU power for it and other resources that affect the server. While hardware raid (HW) is expensive but doesn't use any other power from anyone else. And if their CPU or Motherboard fails on them. That means that the "RAID" will also be affected and in most cases they will lose their data. Blame their datacenter. Bad mouth them and say its their fault. When in reality is the owners themselves for not taking the necessary steps to insure things are safe. But nothing is 100% not even RAID10 is just a pre-caution. If people really wanted their data insured. They would make backups themselves as well. RAID10 is a must for VPS/RDPs etc.
So before I get more offtopic that is one of big things people avoid knowing. The NL server (SAS15K) have SAS 15K drives while the UK server (6Gbps) has SATA II 6Gbps drives. They are both fast. But in my opinion SAS 15K will out last 6Gbps any day of the year. Not that 6Gbps are any bad. But if you need a hardcore application such as encoding done SAS15Ks are for you. Amongst other things.
I would love to write you a book on how the good the bad of having these servers vs others and such. But the reason the prices are the way they are is because they are both different completely servers. But if you want to know "market-prices" just e-mail any popular datacenter and ask them how much this server costs. Ask for SAS drives (not SATA SAS) just 10K or 15K SAS drives, on that alone you will get a HUGE bill. Mention hardware RAID...huge bill. People don't realize my prices -> with what they have is a bargain. Just re-reading what I wrote..I may consider making a video Q/A. Because I like to go very in to detail.