DTS--> Data Transformation Services 
SSIS-->Sql Server Integration Services
in DTS:Message Boxes in activeX scripts
SSIS :Message Boxes In Script Tasks 

In DTS:dynamic Properties+ActiveX scripts
SSIS :Configurations+PropertyExpressions

IN
DTS:no deploymentWizard
SSIS:deployment wizards are there 

DTs:Limited Set of Transformations
SSIS:huge number of Transformations are available 
DTS:ni BI Functionality
SSIS:complete BI Functionality

Hi,
The DTS and SSIS are both used in SQL Server
Transformations. Th e DTS was used for transformation
purpose upto SQL Server 2000 and SSIS (Including SSAS and
SSRS) are the advanced to DTS and are included in SQL Server
2005 onwards. The capability of SSIS tool in comparison with
DTS is tremendous. This SSIS tool is in competition with
other ETL Tools in the present.The SSIS has lot added
features as per the current requirements.

Internal architect of SSIS is entirely different than DTS 
and mainly designed to achieve high degree of parallelism 
and to improve performance. In Microsoft Business 
Intelligence, Integration services are coupled with 
Analysis and reporting services. It could process thet data 
for Dimension processing and Partition processing.Using 
Data profiling task you could analyze data before 
processing and find out the percentage of null values. 
Using WMI Data reader task you could get information about 
system hardware, software and also network information.
More important, it has great security features like 
password protection, Digital signature, Encrypt with 
password. Even we could secure it using Operating system 
permission and using SQL server roles.

SSIS is really a great!