Ry for next year I will be looking for a 2500 size reel and have also looked at the Rarenium and also the Daiwa Certate (new model).
I am leaning towards the Daiwa as I also have a Branzino which is amazing.
Only 12 months ago I would have automatically opted for the Shimano but now its these new Daiwas thet I look at first.
The Rarenium does have a great reputation though and people 'rave' about them.
I think they're pretty different reels to be honest. There's not much of an argument against the Rarenium with it being so lightweight. The Daiwa will be heavier, but is also a fair bit cheaper. Both will be equally reliable and it's probably only a consideration between preferred weight to match the rod (getting the lightest reel you can find isn't always the best thing you can do), and the particular feel of a Daiwa (smooth, solid) or Shimano (loose/free spinning).
The Rarenium is probably a better reel, but if you took one step up with the same price difference, I think the Daiwa Tournament Airity would be a better reel than the Rarenium, so in every case you pretty much get what you pay for I think.