The spec of the chart is not correct (taken from Samsung & HTC official site).
Here is the spec for SII
HSPA+ 21Mbps/ HSUPA 5.76Mbps
EDGE/ GPRS Class 12
Quad band GSM 850/900/1800/1900
Quad band UMTS 850/900/1900/2100
And here is the spec for Sensation
HSPA/WCDMA:
Europe/Asia/T-Mobile US: 900/AWS/2100 MHz
Quad-band GSM/GPRS/EDGE:
850/900/1800/1900 MHz
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It's a HSPA+ vs HSPA and Tri-band UMTS vs Quad band UMTS (extra 850 band for use in Australia/Canada/USA/S. America)
My SE X1 rom-> http://forum.xda-developers.com/forumdisplay.php?f=471