I'd say the choice really comes down to how you like to play: Splendor is one of those games you learn in two minutes and you're already having fun, while Dominion demands more card reading and time to understand the mechanics. What nobody mentions is that Splendor, despite being simple, gets stale pretty quick on replays if you don't have expansions too - so it's not really "buy it now and you're done," it also ends up asking for more purchases down the line. If your plan is to spend money once and call it quits, Dominion might be the better investment for the amount of variety you get right out of the box, but then you're gonna need patience to teach it and to read through the deck.