The 741xs comes with preloaded excellent charts of all coastal US (and I believe Canada--at least my 1041xs does) and Lake Vu High Def. inland waters--again these are very good resolution charts.
The GPS is the latest 10 hz (vs most being 1 hz--so 10x faster) with both GPS (US) and GLONASS (Russian Satellites) GPS systems.
The redraw time and reception are fast enough so that as long as the boat is moving you will get good overlay for the radar over the chart. I have checked this at both 3knots and 25 knots with the 1041 xs
The 7x1 series, is touch screen--and some like that. I have the 740S (older version, but touch screen, and it is nice.
The xs series communicates with the I pad and i phone, so you can see the same information as on the chart--and this may give you a larger radar image if you wish.
The sonar is good--is it the best? That is hard to say--but for fishing and the down scan, it seems to be as good as any I have seen.
The radar works fine--the 7" , especially if you use half the screen for fish finder/sonar, makes a fairly small screen, but it is a good picture. I went with the 10" because even with half for sounder it is good enough for any poor visibility work. It may get a little crowded with AIS, chart, sounder and radar all on one…But radar alone is a good radar image. If I wanted the best for near targets, I probably would go with Simrad G4. But for a longer range Radar the Garmin is good enough.