What is the advantage using mgcamd 1.38c over 1.35a ?

I have used both, they both do the same thing, but according to the changelog it is patched to clear certain channels as detailed below.

1.38 - Added STN support (Macedonian channels with CaID 0x0616 on 16E)
SH4 binary needs replace.list - see the attached example key files
Fixed Nagra2 Kabel Deutschland decoding - there must be "X: { 18 01 }" in your priority.list to let mgcamd
select the correct ECM pid value corresponding to nagra2 ECM stream. If you still have problems with crashes
on KD channels (especially new E2 images), use previous version of libcrypto.so library in /usr/lib/.

1.37 - Removed this very annoying log message: "[mgcam] read error error 145: Connection timed out"
Added Zee TV support
Small fixes in the ppc binary
Added ppc_old and SH4 binaries
The SH4 binary is based on the version 1.35 and has its own replace.list !!!
See the attached replace.list and example SoftCam.Key files for Zee TV and C+NL (SH4)

1.36 - Added support for ICE EMM stream with both headers (8X 40 and 8X 70)
19.2E Canalsat (022610), 39E ANT1 Europe (021110)
Fixed ORF provider 10
Added support for I*****2 providers: 13E JSC Sports (0x0603), 19.2E C+NL (0x0622), 39E Bulsat (0x0604)
Removed some annoying log messages like: [newcamd] ... new card.... or RSA nagra2 key not found for ID...

Hope this helps.