I'm actually using both products (PS V 3.0 and Returnil 2008 beta) on different machines, along with the other options in this category (Shadow Defender and ShadowUser Pro) just to get my hands around the approach and to develop a better sense of it.
In terms of active support by the vendor, PowerShadow
are the clear leaders with the primary difference being that PowerShadow's is via their dedicated support channels (Email, Windows Live IM) and while Returnil's is a combination of forum, email (I assume), and PM.
Currently, all of PowerShadow's support is provided out of Beijing, so you'll have to contend with time zone differences. Fortunately, language is not an issue for English speaking customers, their communication skills are excellent and the time zone differences are not terribly bad for North/South American customers in that the Beijing workday coincides with evening hours in these time zones (they are 13 hours ahead of East Coast US time for example).
Returil has support coverage in the US and Europe and it's been very responsive to date, as any member can note by examining the relevant threads on this site.
While the main function of these products are the same, they do have somewhat different implementations and minor feature set differences:
- Returnil currently protects the system partition only, while PS has two different operating modes - one for system partition protection and the other for protection of all non-mobile volumes on the systems. System partition protection is clearly the most critical facility.
- While operating in protected mode, one is able to commit changes to the system partition using the File Manager facility in Returnil 2008. The specific folder to commit, as well as those changes, can be dynamically handled while in shadow mode (Shadow Defender is similar in this regard). There is an analogous facility in PowerShadow while in Single Shadow mode that uses a folder relocation, but this has to be done prior to entering shadow mode and physically relocates the folder to an unprotected volume (single shadow mode only)
- Both products can enter shadow mode without a restart, and both require a restart to exit shadow mode. Neither carry shadow sessions across restarts (as is possible with ShadowUser Pro, but ShadowUser Pro requires a restart to enter shadow mode in the first place).
- Pricing on these products could be a little clearer. Returnil 2008 is quoted (see here) as $24.95/yr. I assume the subscription model is similar to that for the business product and provides for any software upgrades and dedicated support during the subscription period. PowerShadow's cost is a little higher ($39, although the base cost is supposedly $49, there 20% off at the moment), this covers support via email and minor version updates and bug fixes. Presumably a major version upgrade would be available at reduced cost. In my own experience, the long term differences in these pricing models are inconsequential. Both prices are for single PC's.
- As noted in the thread Returnil Passes Sector Editor Test!, the current Returnil 2008 beta build (22.214.171.12421) now protects against low level sector edits using Julie Lau's Sector Editor (available on plenty of Asian sites, use http://www.google.com/search?hl=en&q...37&btnG=Search and be cautious). I tried a similar experiment with PS V 3.0 using Sector Editor V 126.96.36.199 in single shadow mode. Rather than allowing the changes, and then restoring them on a restart, PS blocked the application from performing any write - shadowed or otherwise. Rather than block fills, I used simple manual edits (although either operation is blocked).
There are some additional minor differences. Both products are young and how the vendors approach specific issues now (specific implementation, pricing, licensing, support, etc.) could change depending on demands in the marketplace. As far as I can see, both products are quite stable (as are the other two options for that matter), function as advertised, have good support mechanisms in place in the event of problems, and both are worth further examination by anyone interested in this application area.