It is a question of record count, update/refresh speed and performance. If you want to refresh Bloomberg fields in Omniscope on a manual as-needed 'pull' basis, using the Data > Refresh Bloomberg data should perform well enough. When you first import Bloomberg fields into Omniscope, you may have to refresh manually a couple of times to fully populate the file. Because auto-refresh from Bloomberg has not yet been implemented in Omniscope, if you want to refresh a very large number of records on an automated 'push' real-time basis, use Create Bloomberg spreadsheet to generate a stand-alone Excel automatic price-monitoring spreadsheet that will perform better. This may change in future.

For more information, see the User Guide section on Working with Bloomberg