I am no expert on either one. I own an Aera 510, and it works great for me. A friend of mine has and uses a 296 and had offered to sell it to me several times for $500.00 before I bought my 510.
He does still use his 296 and seems to like it. It is probably correct to suggest I don't know squat about it. My thinking was that the price asked seemed a little high for such an old unit, but it appears I am wrong.
John