The question of whether or not to use a web FTP service versus a local FTP program depends on what you need to accomplish. A web FTP service allows you to use your browser to upload files to the web FTP service then can upload it to whatever sites you want to. While with a local FTP program you simply upload files from your computer directly to the web servers you want.
Con’s of web FTP services
When using a web FTP service you have to trust your service provider to not have security issues. When you are using a web FTP service you are trusting that provider to have tight security and won’t compromise your files or credentials. If the web FTP provider has a security issue than someone could be downloading all the files you send to the web FTP provider’s servers. If the web FTP provider has their login system compromised than your passwords and credentials for logging onto your server would be compromised also.
Pro’s of web FTP services
You do not have to install a software program to upload files to your server. The credentials for the server you are sending files to are kept with the web FTP service and not on your local computer. You can be mobile and upload files to your web server without worries about someone snooping on you. You can be using a guest computer and can successfully upload files to your server without worrying about having to install an FTP program on the local computer.