Over the years I've tried different brands and used different steel, high carbon and high speed, but the best by far are carbide tipped blades. It's not just that the blade lasts a very long time (my last one lasted 9 months of light daily use) but it's the quality of the cut. The teeth are ground in the same fashion as table saws blades and are all in line, unlike other bandsaw blades where each tooth finishes in an outward facing point.
I ordered these (for my Startrite 401) yesterday afternoon and they arrived this morning! They came from Harrison Saw and Tool 01706 225221 and cost £114 inc vat each for a 3850 mm blade. That might seem expensive but I used to buy the Lennox Trimaster blades which are over £200 for the same spec. The teeth are nicely covered and you can keep this on until the blade is fitted but not tightened.
The blade I use is a 2/3 tpi which may seem coarse but because of the in line teeth it cut very smoothly indeed. Pictured below is my blade guide setting which you can see has plenty of clearance either side of the blade. This may be against all advice but if you have really good tension, a sharp blade and you don't try to go too fast, the blade will cut as straight as a die even to the full 16" depth of my saw.
Here's the English burr walnut for one of my box lids cut to a depth of 14" in about 30 seconds. The finish is good enough to go straight to the sander.
Although I only needed a piece 14" wide I was able then choose the best position to make the cut. I used a negative template of the area required which I marked out when I was happy. This is a great technique which can be used with a mirror if you want to find the best book match.
This is the Burr brown oak which came from Yandles.
Here's a close up of the finish you get with these blades
This is the Claro walnut