If you're going to be trying some demos, I'd say keep notes on whatever you sample, including string info.
Feel is a very subjective issue, so whatever you prefer may be different from what might be considered as more inherently arm-friendly in general. Even if a certain racquet model has earned a very arm-friendly reputation, that's not helpful if you can't use that racquet. Even a softy will be rather harsh for you if you rack up lots of mishits with it.
The comfort and arm-friendliness of any racquet will also be substantially affected by the string type and tension. The Babolat Pure Drive is considered to be rather stiff and not especially arm-friendly, but it can become a MUCH more cozy player if strung with natural gut. Installing a full bed of stiff poly at rather snug tension can make any racquet substantially harder on the arm regardless of its flex rating or shock reducing technology. If you want comfort in any racquet, be mindful of its string layout.
Depending on what you have in your Bio 300, consider dropping tension of trying a softer string type. If you're strung with poly, a bed of basic syn. gut at moderate tension might make a solid difference for you. Multifiber is generally even softer, but I don't use that string type too much. I get decent comfort with less expensive synthetic gut and I like its performance, but multis usually soften at a steady rate for me and become unplayable before they break.
Weight and inherent stability can also contribute to a racquet's "comfort level", so that's something else to consider with your Dunlop. If you want it to play a little more "solid", you could add just a few grams to the hoop using lead tape to see what that gives you. If you don't like it, just peel it off. If you demo other gear, don't be afraid to try something a bit heavier that might do a better job of "winning the collision" with the ball. As long as you can handle the extra heft okay, it might seem quite comfortable for you. The truth is in the demos!!
