Every manufacturer has there own way to build and describe a heat exchanger and the design of tubular vs stamped vs tubular/stamped hybrids is not the most important fact. The metallurgy and grade of steel that they use is far more important. I suspect some el cheapo builders grade units are using recycled metal and pop cans as the metal gets brittle and cracks prematurely. Goodman uses a tubular heat exchanger as well as Rheem. Suprisingly enough Rheem is a middle of the road priced unit and I have never had a heat exchanger failure from them so that design is good. They are a bit lighter built and noisier but a decent furnace for the money. Trane is the most expensive but good and you get what you pay for IMO. Welded vs non welded in not a big issue, the quality of metal is. A tubular heat exchanger is like a S and therefore can expand and contract easier like an acordian but the others expand sideways easily. LOTS of heat exchanger failures are from overfired units where the gas pressure was never set at startup or units running too hot from undersized ducts, dirty filters, dirty AC coils etc etc.