For me Steam Park is the best of the three. Instead of over staying its welcome I actually feel like i need a few more turns to do everything I wanted to do to my park. And the cards are fine. There are more than one of each card and they just give you some direction for what to shoot for. As for Blueprints it is fun and simple and that is my main gripe its just to simple. Not sure if I like the bonus cards in this one because you are not forced to build your blueprint so you can just go for the bonus cards. The only thing I will say for Cv is you are right not many decisions and I have had my fill after two games. I just ordered Castle Dice and should have it by the weekend so if you are still deciding I can post and give you my thoughts on that one too.
I've played Blueprints and own Castle Dice, CV, and Steam Park.
I did not like Blueprints but I only played once in a 2-player game. I don't like how all the bonus cards are worth 2 points in a 2-player game, making it obvious exactly how many points your opponent has. I don't see the point in keeping the scoring cards hidden in that instance. I also never really found the decisions all that interesting. It always seemed like there were certain goal cards you should aim for based on what building you have that round. It's not a bad game, but it just didn't do it for me.
CV has much more interesting decisions, IMO. After a couple rounds as you've purchased cards from the display and you have symbol tokens and special abilities, it becomes very tough to decide if you should stop rolling the dice or take a chance to roll what you really want instead of settling for what you can definitely get. And you really do feel like you're trying to make life choices that you can't always make due to external forces beyond your control. My wife and I like CV a lot. The whimsical artwork helps quite a bit. It is a lighter game than Steam Park and Castle Dice. I do think 4 players is too much for the game as turns can take a little long while players are internally debating which cards to go after. If you're tolerant of longer turns it might not be an issue for you.
Steam Park might be the prettiest game I own. And the cardboard rides are simply delightful. The frantic dice rolling each round is a lot of fun and there is a deceptive amount of strategy in how you plan your park, which rides and booths you buy, and how you manage the dirt you accumulate. I haven't felt that any bonus cards are unbalanced. If it turns out there is an unbalanced bonus card you could always remove it from the game. Unlike CV, Steam Park is better with 3 and 4 players. It's still good with 2, but better with more.
Castle Dice has more luck than Steam Park and CV (once you get some cards in CV and have symbols to use). You'll find it hard to build some of the castle cards if you can't protect your resources, and you can't protect your resources unless you pull and hire guards from the deck. There are a lot of interesting choices to make each round, but I've seen games where it was obvious who was going to win just by who managed to get some guards early in the game. I still really enjoy Castle Dice, but I do wish it was a little less dependent on luck of cards draws. It plays well with 2, 3, and 4 players.
So that's my take on these 4 games. I don't regret buying CV, Steam Park, or Castle Dice and I don't regret passing on Blueprints.