The variable in the Y pipe for performance is minimal. Akra, Scorpion and MJS have a very similar bend. Only Yoshimura has a very different bend in the Y pipe. But they don't sell a linkage pipe alone. You have to buy the 3/4 which gets excellent reviews. If you look at the bend, you can see why, it does have less turns and longer linkage piping.
Either way, I wouldn't kill yourself over the linkage pipe. The big factor is getting rid of the CAT and TUNING it. Those go together. Get rid of the CAT without a tune? It will lose power I guarantee you. I rode my bike in between upgrading. You have to add more fuel with adding more air.
Pretty much any linkage pipe or 3/4 is WITH a tune will blow your mind. Just for an experiment, I used the MJS linkage pipe and stock canister with block off plates and SBU flash. God damn.
I'd worry much less about the brand of Y pipe, and worry more about the tune and block off plates.