The chips are different and the screen resolutions are also different. In addition to basic video formats, such as MP4 FLV, T7 can also perfectly support 720p WMV AVI RMVB. The 800×480 screen resolution is clear and the colors look great. The T17 has a resolution of 480×320, does not support WMV, but supports MKV. The video and sound effects are slightly worse than those of the T7. If LZ has demand for MKV video sources, go for T17, otherwise go for T7. There are quite few MKV video sources on the Internet compared to RMVB AVI. Except for MKV, T7 is better than T17 in all aspects. Bookmarks are supported.