Today the blogosphere and social media world is all hot and heavy for Foursquare, the NYC-based location-based check-in company, given its latest release. The mobile app’s new release allows users to add pictures to and comment on check ins at the venues, stores and other locations you visit — something that has long been core to Boston-based SCVNGR’s location-based app. Needless to say, the check in wars are on here in the Northeast.

SCVNGR, which touts creating a game layer on top of the physical world, includes more feature-rich game elements — like challenges as specific locations beyond check-in and full blown “treks” across multiple locations. Foursquare, on the other hand, benefits from its early mover advantages with a larger user base. Given the social nature of check-ins, Foursquare’s larger user base (5 million vs. SCVNGR’s 600,000+*) provides network effects that may compel people to engage more. Both companies are going after the loyalty and rewards space, and to date SCVNGR seems to have moved more diligently in offering more discounts and rewards to its users (particularly here in their home city of Boston).

We put these two check-in apps against one another to compare photo sharing features (screenshots included):

Checking In with a Photo

On SCVNGR: Once your venue is identified by GPS or search and selected, you are taken to a page with various challenges to perform at that location. “Check-in” and “Snap a picture” are two such challenges. Another is the “Social Check-in” which allows you to check in with other people (in SCVNGR gameplay this means you earn extra points by a multiple of the number of people checking in).

On Foursquare: Once your venue is identified by GPS or search and selected, you are taken to the venue’s page which prompts you to click “Check in here.” The next page allows you to add a photo and comment to append to that check-in.

Sharing Your Photo Check-in

When sharing your photo and checkin to Facebook and Twitter, both SCVNGR and Foursquare share the same elements (location, link to photo, comment), in slightly different ways. SCVNGR underscores the apps gaming elements, placing the challenge or points earned front-and-center while Foursquare focuses more sharing location info. For people clicking on your shared check-ins, the link brings you to a page that looks like this on SCVNGR and like this on Foursquare.

Viewing Friends’ Photos

Both applications include a feed of friends’ check-in activity. Each check-in is displayed in the feed with the person’s profile pic, location, timestamp, and any comment provided. In both applications, you can comment on the photos your friends are sharing from the friends feed.

The big difference between the feeds is that SCVNGR also aggregates any activity from friends (not on SCVNGR) who are using Facebook Places to check-in.

The other obvious difference is that SCVNGR displays a thumbnail of the photo directly in the feed, while on Foursquare the camera icon displays blue if a photo is attached and clicking on it brings you to viewing the actual image.

(*SCVNGR user number estimates above are based on the ID numbers associated with a users individual profile, e.g. I am http://scvngr.com/users/191906/). The company publicly announced passing the 500,000 user mark in mid October.)

What other differences matter to you about these location-based apps? Leave your thoughts in the comments!