I have used all of the above. SPringfield leather gets more of my business than most. Great service IMHO
I had mixed results with Springfield's leather, mostly good stuff. My problem was more with errors in orders, backorders, and billing issues.
Tandy's leather, was usually dirty, scraped, and fully dependent on the packer's mood. I am not driving 4 hours to Atlanta, but, if you can actually lay hands on the goods to select, you might do ok. However, better leather can be found, and at a better price . Springfield does usually have better goods, but the big difference is, Springfield will cut to order, where most require you buy the side.
I'm trying a new place, somewhere up in Yankee country. Last double shoulder was pretty clean, and buttery soft. Price was about $80. I asked for a straight cut along the long edge, and it looked like my grandchildren attacked it with safety scissors.
Tandy has a sale on double shoulders right now, about $40. Again I asked for a straight cut, and got it. The leather had some flaws, but not terrible, but not as clean and soft either.