Atari 7800, XEGS, and ST questions

[Rob2600]

1. Does anyone know which Atari console had better graphics capabilities, the 7800 or the XEGS?

2. Why did Atari release these two home game consoles within a year from each other? Why would they choose to compete with themselves?

3. Why did Atari chose to adapt its 8-bit 65XE computer into the XEGS console? Wouldn't it have made more sense for Atari to adapt its 16-bit ST computer into a console instead? I've never used an Atari ST computer, but judging from screen shots, it appears to have had graphics on par with the Amiga and Sega Genesis.