Am maintaining accounts with Turkish, Singapore and Air India n normally redeem to/from Europe and Delhi.

Turkish redemptions are 90k one way in business. Recently used United 12.5k miles on Geneva Istanbul sector in economy and onward Istanbul Delhi sector 50k Turkish miles in business. This also lowered the Taxes substantially.

Air India redemptions are 90K miles one way in business but taxes are nominal. Also have to fly 2 paid sectors (domestic or international) on Air India before an award ticket can be issued. Currently all Award redemptions on Air India are discounted 25%.

Singapore redemptions to Europe in business are 62k one way and taxes vary depending on the star alliance partner. A sweet spot is 78k miles for a Delhi to Bali return redemption ticket in Singapore airlines business.

I check options in all 3 programs. No hard and fast rule which program will offer the best deal. You will need to credit a few miles in any program before checking options.