This information leads me to think the unlock version will work with Sprint 4G, but I am not too sure about 3G:
HTC U11 Unlocked Band Support4G LTE (up to 600Mbps download speed/with 2CA, 3CA Carrier Aggregation and 256 QAM, service dependent): FDD: Bands B1/B2/B3/B4/B5/B7/B8/B12/B13/B17/B20/B25/B26/B28/B66 TDD: Bands B41 with 2CA, 3CA, 4CA Carrier Aggregation 3G UMTS: 900/850/AWS/1900/2100 (B8/B5/B4/B2/B1 with 900/850/AWS/1900/2100 diversity), HSDPA 42, HSUPA 5.76 2G/2.5G - GSM/GPRS/EDGE: 850/900/1800/1900 MHz