If the tension seems greater with the 4 knot (two piece) guy, I'd ask what kind of machine they use and compare to the other. You may be strung on a different tensioner type, which would be a systematic inconsistency (not a bad thing, they're just different).
What frame are you using, also? It may void your warranty to have a frame strung with one piece, and COULD possibly indicate the level of care your stringer gives your equipment. Wilson/Babolat frames are OK to string bottom to top (officially), and most racquets have main (vertical) strings that end at the bottom of the frame (which implies crosses [horizontal strings] are strung bottom to top, which can be a warranty void situation -- although to be fair, I've never actually seen this happen).
4x Dunlop Bio 200 L // Babolat Sensor
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