Mouse over GAME INFO at the top of the screen and choose ship tree, select Royal Navy and scroll to the far right of the ship tree beneath. There, you can see all of the details for all of the RN event ships including the Valiant EBB3 and the Hood EBB4.
The Valiant is a Queen Elizabeth which can use any of the BB3 guns but is most commonly seen with the 16" triples from the Nelson for the firepower. It's level 78. It's an EBB3 which basically means its a very strong BB2. You could use it instead of an RN BB3 (The Hood, Nelson or PoW) but since those ships are mostly better aswell, you're more likely to replace them. But that's up to you, the firepower of the Valiant is very good though, better than any BB2 or BB3, the biggest problem with it is the spread of the 16" guns can be pretty bad without high level gunners.
The Hood 1939 is a Hood which uses the normal Hood guns, it's level 86. It's an EBB4, so its a strong BB3, you would use it as a ship to help level toward BB4 and similarly to the Valiant you could use it instead of the BB4s for a while, but since the BB4s have gun upgrades over the Hood 1939, I wouldn't recommend it.
I'm not sure about their speeds but the Hood is quite fast and I think the Valiant is about average. Like all EBBs they are slightly stronger than their base ships is almost every way by small amounts and they have an extra support slot to add some strength and to make them better for leveling with.
You should check the guide I wrote about all the event ships for the current event aswell.