Samsung Galaxy S6. Source: Samsung.

Buyers of Samsung's (NASDAQOTH: SSNLF) latest flagship smartphone, the Galaxy S6, may be missing out on a few of the handset's potential features.

In the U.S., all four major carriers -- AT&T (T 1.10%), Verizon (VZ 0.90%), Sprint (S), and T-Mobile (TMUS 0.92%) -- appear to have made modifications to the device. While most are modest changes, some are more significant, and all serve to highlight a key advantage that Samsung's chief handset rival, Apple (AAPL -1.22%), still holds over the Korean tech giant.

Blocked features, missing apps
Although Samsung uses Google's Android operating system, it built a number of unique software features into the Galaxy S6, some of which could be quite useful. These include, among other things, a TV remote app (Smart Remote), a power saving mode, a way to rapidly send files (Simple Sharing), a device diagnostic tool (Smart Manager), and a way to speed up file downloads (Download Booster).

To be clear, most of the Galaxy S6's features have been left intact, but a few are missing. The AT&T version of the Galaxy S6, for example, excludes Samsung's Download Booster, Smart Manager, and Simple Sharing. Verizon has also cut Smart Manager, while Sprint has removed Download Booster. To its credit, T-Mobile has largely left the device intact, but appears to have made some odd modifications to its settings (users cannot disable particular features, or remove S-Finder from the pull-down menu).

The biggest change may be the removal of Microsoft's (MSFT -1.27%) preinstalled applications. Ahead of the Galaxy S6's unveiling, Samsung agreed to load many of the Windows-maker's mobile apps onto its device, including Office, OneDrive, and Skype. But the carriers have gotten in the way -- a Galaxy S6 purchased through Verizon has no Microsoft apps whatsoever, while one bought at AT&T is missing OneDrive.

This decision may actually be beneficial to Samsung's customers, as it reduces the overall software bloat on its handsets. But the preinstalled OneDrive application offered 100GB of free cloud storage -- a nice perk any Galaxy S6 owner would be happy to have.

Why did the carriers make these changes? Some of them seem entirely inexplicable. Others could be attempts to drive greater adoption of their own competing services -- both Verizon and AT&T offer cloud storage services, for example.

Apple refuses carrier modifications
This stands in sharp contrast to Apple's iPhone, which is largely the same regardless of the carrier it's purchased through. An iPhone bought through Sprint or Verizon will come preloaded with identical apps -- and no carrier bloat.

This has been Apple's policy since the iPhone's introduction, and it's one that's certainly benefited users. The modifications carriers make rarely result in an improvement in the user experience -- they almost always make the device less appealing. In particular, preloaded apps often duplicate existing functionality in occasionally unscrupulous ways. Verizon's VZ Navigator, preloaded on the Android phones it sells, offers an experience virtually identical to Google Maps, but unlike Google Maps, it costs money to use.

An unsuspecting user, otherwise ignorant of Google Maps existence, may wind up paying additional money for what's truly a basic feature.

No Download Booster probably isn't a dealbreaker
Ultimately, I doubt these modifications will result in any lost sales for Samsung. The changes are far from significant, and dedicated users with a level of technical know-how can get around them. Microsoft's apps -- including OneDrive -- can easily be downloaded from Google Play.

But it's an issue of quality, and it's still a major area where Samsung lags behind its chief rival. So long as carriers continue to mess with Samsung's handsets, some buyers on the margin may be swayed to Apple's iPhone.