1:600 Exeter, as she was in the River Plate battle. 4" AA are paired, after funnel is thickened and an amphibian is carried on the catapult. © Andrew Arthur

These two ships were a "B" Class diminutive of the "A" or "County" Class heavy cruisers, a 25% reduction in main armament producing a commensurate reduction in cost. Although 7 ships were originally planned only two were built because of successive cutbacks in defence spending.
While their particulars were almost identical, they differed in appearance: Exeter had straight masts and funnels, while those of York were raked. Moreover, Exeter's bridge structure was of the "box" type (next seen in the "Leander" Class light cruisers), while that of York was a smaller version of the structure in the "Devonshire" Class.
This was because York had been designed to carry a catapult and amphibian on "B" turret, but, when the turret proved to be too light for this arangement, the tall bridge to obtain a clear view over the plane, and raked funnels to keep smoke out of the bridges remained.
Both ships had short careers in World War I, Exeter being best remembered for her participation in the Battle of the River Plate which led to the scuttling of the German pocket-battleship Graf Spee.
They were the last Heavy cruisers built for the Royal Navy.

Pictures of York class Heavy Cruisers

HMS Exeter