Couple of things to think of.
What drop are the brakes you need to improve. Bikes with mudguards often have calipers with longer arms than a race bike. Shallow racing brakes have a drop of 49 or 50mm. Medium ones 57mm. You need to measure the drop you need for your frame. Bear in mind that the leverage on shallow drop brakes is more so if your winter bike needs medium drop brakes their performance won't be as good as a your other bike even with the same make of brake.
Brake blocks make an enormous contribution to braking performance, more so than the make of caliper. Find some good ones - Swissstop, Koolstop, Aztec and see if these make a difference.
Tektro brakes aren't necessarily bad. I've had brakes that were rubbish - too much flex in the arms - and replaced them with Tektro ones to good effect.