Although the SharePoint 2010 BCS External List is a great step forward with SharePoint data integration, it is not a REAL SharePoint list - as the SharePoint BDLC List definitely is. That causes some limitations.
First not all BCS features are available in all SharePoint editions:
| BCS Feature |
SharePoint Foundation |
Standard Edition |
Enterprise Edition |
| External List |
 |
|
|
| External Data Column |
|
|
|
| BDC Service |
|
|
|
| Connector Framework |
|
|
|
| Secure Store Service |
 |
|
|
| External Data Search |
|
|
|
| Profile Pages |
|
|
|
| Business Data Web Parts |
|
|
|
| Rich Client Integration |
|
|
|
Read more about this here:
http://www.chakkaradeep.com/post/What-is-Included-in-BCS-e28093-BCS-Feature-Comparison-Table.aspx
The next table compares a SharePoint BCS external list to a real SharePoint list, that is connected via BDLC:
| Feature |
SharePoint 2010 External List |
SharePoint BDLC List |
| Integrate external data from various sources into SharePoint |
|
|
| A complete SharePoint list with all list features is implemented |
|
|
| OOB almost any type of data source is supported |
(.NET Type / WCF Service / SQL Server) |
(more info) |
| Full SharePoint 2007 / WSS 3.0 support |
(SharePoint Foundation 2010 supported) |
|
| No additional tools, modelling or programming are required to create a list |
(SharePoint Designer has to be installed and used) |
|
| Connection can be established in just some minutes |
(more info) |
|
| OOB full search capabilities |
 (not for SharePoint Foundation) |
|
| Full Offline capabilities |
(2010 Enterprise only) |
(with SharePoint 2010 only, SharePoint 2007 supports certain list types only, e.g. contacts) |
| Full Info Path support to customize forms |
|
|
| OOB-support for the SharePoint Client Object Model |
|
|
| OOB-support for REST-services web part connectivity |
|
|
|
OOB-support for making associations to other SharePoint lists
|
|
|
|
Event-triggering
|
|
|
| Alerts will be fired on data change |
|
|
| Email notification on data change |
|
|
| RSS notification on data change |
|
|
|
Workflows can start business actions on external data change (SPD, Visio, VS and Nintex-based)
|
|
|
|
Datagrid editing supported
|
|
|
| Lookups can display any column |
(ID Only) |
|
| Support for joins as data source |
|
|
| Support for common SharePoint list types, e.g. contacts, tasks, events etc. |
|
|
| Exel export feature |
|
|
| Item level permission |
|
|
| Versioning |
|
|
| Item history |
|
|
| LINQ support |
|
|
| Site column support |
|
|
| Rating support |
|
|
| Commenting support |
|
|
| Tagging support, Activity Streams etc. |
|
|
| Managed Metadata and Enterprise Keyword Columns |
|
|
| Metadata Navigation |
|
|
| Attachments enabled |
|
|
| Anonymous Login support (for public facing sites) |
|
|
| Office 2007 support |
(2010 required) |
|
| Works with all 3rd party Add-Ons |
|
|
| Original data source is not queried every time the list is displayed with performance side effects |
(some kind of cache seems to be implemented) |
|
| Data is available on site while original data source is not available (e.g. for maintainence) |
|
|
| OOB there is no row limit |
(it seems to be a row limit of 2000 preconfigured, more info) |
|
| Data source can be updated (if primary key available) |
(for a very few data sources only) |
(if supported by data source) |
- feature included out-of-the-box
- feature partially included
- feature not supported
Read more about the BCS features compared here:
http://www.chakkaradeep.com/post/BCS-Limitations.aspx