We use Survey123 Connect, Field Maps, and a combination of the two. The answer to your question depends on what you want to do. If your data collection is more information and not so much feature delineation, Survey123 is easier and more accessible to users. If your data is more map centric, Field Maps has advantages. However, Survey123 has also come a long way and users of Survey123 can now create points, lines, and polygons on maps. If your survey is more question centric about existing features, then Survey123 may be better. Survey123 is much easier to use (in my opinion) and the survey forms have more options than the Field Maps smart forms (though ESRI keeps updating these apps and adds functionality). One issue with Field Maps is you cannot have a user select multiple options on a field. This is one reason we incorporated survey123 forms into Field Maps. Note also, learned the hard way, that not all functions of available in Survey123 work when using Survey123 integrated into Field Maps. Grids is an example. Survey123 Form custom colors and other formatting is also not available in Field Maps. The other issue is if you are having the public collect the data, users of Survey123 don't need to have an ESRI account. Field Maps requires users to have an account to access the app. Also, if you are collecting data where you may not have internet connection Field Maps works well with offline maps. Survey123 Field App supports offline maps also but Survey123 Web App does not. Survey123 Connect allows for more advanced features on your survey vs Survey123 Web App. We also found that if you use Field Maps App to collect on the ground data (we were collecting shoreline feature data), an external blue tooth GPS unit is helpful to improve the accuracy of the location data. If using the phone/tablet "GPS", accuracy can be quite low depending on where you are. I would start reading about the Field Apps and watching the Videos on YouTube, you can really learn a lot from the videos.
