1. The i5 will probably be faster despite having half as many total cores. The extra ram of the AMD could be useful for some things though.
2. A dedi with just one disk (no RAID) is scary, especially on that older server where the drive may already be beat to hell. It's one thing if you're using it as a cache replicating data that already exists elsewhere, but for general use I'd definitely add a second drive. Software raid 1 works fine.
3. OVH issues just one ipv4 address to those cheap servers, though there's supposedly some "failover" trick to get 3 addresses. If you want more, you have to pay for the "professional" package. I don't know if you care about this. You do get a /64 ipv6 block if that turns you on.
4. OVH is notoriously intolerant to any sort of abuse including inbound DDOS. They cancel ALL your servers if that happens, from what I've heard. So I couldn't see hosting random people's VPS's on them or doing anything likely to attract attacks. For quiet personal use, they are great.
5. I wonder if it might be possible to upgrade the hardware of that AMD box, by buying 4-core or larger CPU's on ebay. It's likely that there are drop-in replacements (depending on socket type) for the dual core cpu's. Since they are still obsolete, you can sometimes find them dirt cheap.
6. OVH network capacity is tremendous. I've done multi-hour (50+ GB) outbound transfers (Quebec to NY) and really kept up the full 100Mbit/s the whole time. This is from the KS1 plan (dual core i3-2130, 8gb). I now also have the SP1 you mention and it's great. It runs my application about 1.7x faster than the i3, if that matters. This reflects the relative passmark scores pretty closely. But, it's desktop hardware, has non-ECC ram, etc. The AMD box is maybe more "serious" though older.
6.5 (added) One annoying thing about the cheap OVH servers is that the INTERNAL network interface is capped at 100 mbit. I can see limiting the internet bandwidth to that, but it is chintzy to have transfer that slow to other boxes in the same data center. It took around 24h to transfer 1TB of data between two boxes because of that. Their more expensive servers do have gbit ports.
7. I'm really surprised at the low hosting cost for something as electricity hungry as that quad socket AMD. It probably uses over 4 amps of power when fully loaded. Power in DC's is at a huge premium these days, so most of those boxes are retired.
If you are ok with European location, you could also look at Hetzner servers including from their online robot.