Do they share any accessories?
I can't answer this part but while it's certainly one way to decide on what to get even if they do I don't think it should drive the final decision.
I think the way to approach a purchase like this is to honestly assess how much future use the 1/2"-collet router is going to see in your workshop given you already own a trim router — so many workshop duties are well covered by trim routers, and cordless ones add an extra layer of handiness that's undeniable once you see them being used.
This isn't to decide whether you want/need a router that can take 1/2" bits, that need is already there, but to help decide how far up the food chain you need go in the larger router you select. If the price differential is significant enough for you to be asking I suggest a realistic assessment of how much use the larger router will get is called for.
Some people say it's always wise to buy the best you can afford, essentially "buy once, cry once", and there is obviously something to that, in both hand and power tools. But the reality is that it has never been the route to best value, much less the assurance of quality it is claimed to be. And the falling standards of almost all power tool brands over recent decades has further chipped away at this argument -_-
So in recent years there has been a rise in the "buy cheap/cheaper, see how much I actually use it" camp. This has a few advantages you can probably think of yourself, but sometimes there's a pleasant surprise in store when you discover just how good a tool is even though it's one or even a couple of rungs down the ladder!