dynamic content faster due to shared data frameworks, caching, indexes, code
2. Security
static content more secure
more resistant to DOS issues
one entry point for dynamic functions
more security levels, roles
more granularity in assigning access
groups
grant and revoke permissions
3. Feature Consistency
any content can make use of any CMS features that are useful
consistent translation, sorting, search, formatting, pricing, tagging, workflow, metadata, etc.
consistent security rules
consistent publishing
4. Ease of learning
due to feature consistency, learning a feature in one module means you've learned it for all
eg. translation, pricing, publishing, configuring
5. Simplification
simpler, cleaner URLs
no need to decide whether content should be static or dynamic
simpler management of web forms, registration fees, product catalogs
6. Leading Edge Web Standards - HTML5, CSS3
responsive
BootStrap
multi-size content views
accessibility
7. E-Commerce
smarter shopping carts
standardized price handling
reporting improvements, GL codes
general-purpose order forms
8. Workflow
save as draft
queuing, scheduling
hourly, daily, weekly publishing
moderation tools
tasks, todos
form workflows
9. Miscellaneous V3 limitations and annoyances overcome
file size limitations
tagging (tag anything, multiple keyword indexes)
linking to non-page URLs (eg. documents, 3rd party sites) from menus
10. Extensibility
easier to spin off new content types and custom modules that automatically get all this
faster, cheaper, more reliable custom development
Many more reasons, too...
more layout and templating options
stronger social media integration
more URL and linking features, including dated friendly URLs, documents and 3rd party sites in menus, options to hide from search and robots
more translation features for multilingual websites
new search features, including module-specific searches, search integration to admin control panels, and controlling what can be searched through your own site search and by 3rd-party search engines
all-new modules for registration, membership management, event management, forms