Knowing I already own Crusader, is there any reason why I should get Stronghold? Both games look extremely similar.

Yes, they are quite similar, yet there are some distinct differences. Crusader has some new units and a few (better buildings). Also the settings between the two change some of the gameplay. In Stronghold you usually have good, wide swaths of land on which you can build farms and the like, while in Crusader you're limited to much more restricted oasis patches located on the map. Crusader also introduced a skirmish mode not present in Stronghold, but it's not as important as you can actually grab a shitload of user-created levels here. Lastly, I'd recommend Stronghold over Crusader for newbies because the latter gets tough very quickly for newcomers. Sometimes I just prefer to play in the traditional European medieval setting, but I must say Crusader has an incredible ambiance, which is especially due to its terrific soundtrack.

Whatever you do, stay away from the awful Crusader Extreme version of the second game, as it added some highly unnecessary and quite broken game mechanics to Crusader. The classic version, which is also available in the HD installer, is still your best bet for that one.

That said, I love them both. I really do recommend both, but if you only want to get one right this minute Stronghold should be the one. You can give that a try and if you like it enough you can still come back to nab the other one from the sale until the New Year. ;) One last thing: if you're interested in multiplayer you're in luck! Both Strongholds are of the rare older game kind that still have quite a happening multiplayer scene (more so for Crusader than Stronghold) which you can find on GameRanger.

Thank you!

Yeah I've played through 4 missions in the 1st Crusader campaign and it was a bit tough sometimes. This is actually my first RTS since Myth (and I wasn't even good at it) so I'm not sure I will ever try the Extreme game, the basic one seems challenging enough as it is.

Maybe Stronghold would be best for me to start with then.