The Following are the differences :-
a) Multiple page formats are possible in smartforms which is not the case in SAPScripts
b) It is possible to have a smartform without a main window .
c) Labels cannot be created in smartforms.
d) Routines can be written in smartforms tool.
e) Smartforms generates a function module when activated.
f) Unlike sapscripts (RSTXSCRP), you cannot upload/download Smartform to your local harddisk.
It was said that it was provided in CRM 3.0 version, but not available in R/3. You can download smartforms into Local PC in a XML format. In the same way you can upload this XML format into Smartform. From the smartform editor itself you can call download option, if you are working in CRM 3.0 environment.
In R3 also, you can download into XML format. However, it's not sure about uploading. Refer to the program 'SF_XSF_DEMO'.
In 4.7 Enterprise, other have seen this utlity which is completey missing in 4.6c. There is functionality to downlaod a complete form or only a particular node. (Utilities -> Download form). It will create a XML file and save it in the hard disk.
For others, if you want to download/upload the Smartforms source, you will need the help from the Basis people. What you can do is to create a Transport and then FTP down to your local harddisk. When you need the Smartform source in another system, you have FTP up the Smartforms file back to the SAP server. Finally, the Basis team, will tp it into your system.
g) The protect and endprotect command in sapscript doesn't work with smartforms. For example on a invoice: First data of position no 80. is printed on page one, other data of position no 80 is printed on page 2. And there's nothing you can do about it. Actually, there is something you can do about it. By using a folder node and checking the 'protect' checkbox, everything in that folder will be page protected.
What is SAP Smart Forms?
Advantages of SAP Smart Forms
A Simple Smartform Tutorial
FAQ on Migrating SAPscript to SmartForms
Conversion of SAPSCRIPT to SMARTFORMS
SmartForms System Fields
Example Forms Available in Standard SAP R/3
Smart forms Frequently Asked Questions