I can not comment on the DSI or ST-5 all I know is that the Toucam, LPI and sac 4.2 is very dissapointing to guide with in Brisbane...thats the reason I went all out on a dedicated guide camera.
The ST-5 should be just as a good but with a smaller chip....Eddie Trimarchi used the ST-5 before going to the ST-402me...so they must be good.
You would also think the DSI should also be an improvement over the Toucam with longer exposures.
But it's not just about longer exposures..I set the LPI to 15 seconds exposure's and still didn't get any of these guides stars.
http://www.astronomics.com/main/SBIG...uct_id/402ME2C