I have been both TK Elite Plus and Aegean Gold for many years. My experience is that both are useful but for very different purposes.

During the past year, almost all airlines have made it very difficult indeed to redeem business class tickets on other cooperating alliance airlines. With TK, it is easy to book X class redemption tickets but the taxes and fees make this a ridiculous prospect since the end price is almost the same as a mileage-earning economy ticket. TK has also made it all but impossible to book I class business tickets on both its flights and those of airline partners. However, availability is still comparatively good for J class business upgrades from any revenue economy class fare (J class is also used by TK as its lowest revenue fare bucket for business). Another big advantage of TK is that E+ cardholders get two system-wide upgrades from economy to business once a year - I normally use these to upgrade a P class BER-IST-BKK-IST-BER return ticket costing around €650. To conclude: TK Miles and Smiles is great if (1) you fly intercontinental at least a couple of times a year and use TK; and (2) you use mileage solely to upgrade revenue tickets to business.

Aegean M&B is great for those who live in Greece or Cyprus, and for those who are not really frequent flyers but want to benefit from *A benefits when they do fly. Maintaining A3*G is also extremely easy and typically requires less that €1k ticket spend per year. And for this minimal spend, you get four A3 one-sector upgrades per year. However, redeeming M&B miles on long distance business tickets is dire: I have over a million miles and always find there is little or no availability, or that the taxes and fees are massively more than those with LH Miles and More (with which I collect about 500k per year). To conclude: M&B is good if you're Hellenic based, don't fly much and don't need intercontinental business redemption flights.

In your position, Sydunipete, I would stick with TK and try to achieve E+ to get the annual two system-wide upgrades. And I would use mileage solely to upgrade discount economy tickets to J class business. And to avoid TK's disastrous IT and poor call centre (especially compared to Aegean's excellent call centre), you perhaps need to cultivate links with your most-used TK airline office. When staff know you, they will often move heaven and earth to help you with redemption bookings.