crystal reports :we use most of the times daily basis.we 
have to know the day to day staus.example daily transaction 
of the persons in a bank.end of the day whole sales reports 
of the same branch.it is for production .it is a predefined 
templete

web I: it is only for manage ment users.
       they want to take own decessions for their own
       like take a sales mall giving offers like end of 
season sale and clearence sales occational offers.

Webi report- it is ad-hoc report, we can modified as per 
request and analysis the reports.

but in Crystal reports--> we cant not modify the reports 
and it contains daily bases i.e., day to day 
infromation .example: shopping mall and customer details in 
bank

Crystal Reports can be when more customisation of the 
report is required. The complexity in creating Crystal 
Reports is more than the Complexity of WEBI.
Crystal Reports formatting requires more effort and the 
look and feel of export may require some modifications to 
fit users requirements.
WEBI can be used for Power Users who can design their own 
reports. However The flexibility on customisation of the 
reports is limited.
Since WEBI is in Columns and Tabular format, there is not 
much formatting effort required.

Crystal Reports: Useful for reports with complex layout
formats, dynamic formatting(like decimals, date formats,etc
), dynamic suppression of the report parts(like sections or
stand alone fields)

WebI: Used for ad-hoc reporting. Easy to modify and analyze
the reports on the fly