Both Admiral level. If Shiryu is stronger, it would be like Akainu v Aokiji difference, extreme extreme diff. Same for EoS Zolo, I don't see Luffy's underling beating an Admiral without being at EoS and without extreme extreme diff fight.
There is no such a thing as BB's morals. BB just wants strong people, that's it. BB wanted Ace in his crew as well, he doesn't care about their morals.
It means Ace and Jinbei, who were equals, fought for 5 days, which is 50% of the time of the Akainu and Aokiji fight, and this coming from two characters who were barely Yonko Commander level?
We could assume that two Yonko Commanders of equal level (YC1) could easily surpass the 5-day mark of continuous fighting precisely because they are superior to Ace and Jinbei.
We saw Jack fight for 5 days straight without a break and he had the full ability to go for a sixth day, and Jack is a Yonko Commander level 3.
With this history in hand, I faithfully say that two YC1, when equal in terms of power, can reach 10 days of battle, like Aokiji, who is a subordinate of Blackbeard, and Akainu, who is a subordinate of the government and the five elders.