Some games (like Super M) uses special audio chipset

Edit: kind folks answered my question by email, carry on please

A Carnivore 2 includes MSX-MUSIC. So, no need to get both.

Personally I think those aren't redundant.

The menu system of C2 is a lot more flexible and the configuration software is really flexible, and it's also compatible even with FPGA MSX models where MFR won't work. With the different menu builds it's even possible to get broader compatibility. Being able to have multiple different MegaROM's flashed at the same time is really handy. The dual-reboot and flexible slot/sub-slot editor capability also makes some exciting things possible using it in specific configurations needed by other ROM cartridges. Also the ability to "take over" unused adjacent slots means those with MSX'es with only one open cartridge slot but an unusable empty slot in the map can suddenly use a lot more features. Being able to conterol the cartridge using a controller in addition to keyboard means it's even usable on an MSX with no keyboard, or where the keyboard doesn't work. Finally, menu music. I know it's a bit cheesy but I like it and actually use it to ensure MIDI-PAC v2 successfully made wireless connection (via Roland WM-1) to synthesizer modules before starting the "real" program

On the other hand MFR requires fewer steps to overwrite the flash and then reboot into that specific flashed ROM, plus its ROM disk booting can be very convenient when you need to partition+format a card, and the option to get it with dual card slots makes it really flexible when dealing with multiple cards or more content than one partition fits (I think maybe C2 is architecturally capable of that also but I never saw a dual-card slot version for sale). Also the ability to change the key codes used for controlling the cartridge from the command line is really helpful especially if your keyboard isn't fully functional, or if your MSX or another cartridge has a colliding boot-uo hotkey assignment.

Actually, I wish to apologize to have given a misconception. I finally bought my MSX 2 after long term of payment installment and it only left it's origin country almost four days ago and it is coming it's way here. So I am beyond excited in this regard. I have not bought MegaFlash SCC but I do love MegaFlash and have been comfortable and find it a superior solution since it also support both ROM and disk drive at the same time. What I did want is the ultimate sound solution so I can enjoy the audio of many games. C2 seem to hold the solution I was not aware of it been also a MegaFlash like content as well. That being said, I like having it too. I consider it a backup in case something happen wrong with MegaFlash but I prefer never to use C2 as form of running ROM or replace MegaFlash since it does not support disk images. I do need to get another cartridge to emulate disk image which means two different cartridges to do what MegaFlash does in one cartridge. Honestly, if there is a cartridge that does support all the audio chipset as C2 plus OPL4 without all the other fancy stuff like internet, flashing ROM or disk, etc and goes cheaper in price than C2 for 50 euro instead of 100 euro I would buy that in a heart beat. I just want the ultimate sound card for my MSX2.

However, if it must include these other features to get it...I will do so gladly.

P.S "But first I want to get MegaFlash! I am saving money to spend 120 euro and get MegaFlash SCC. After that, I will get the other cartridges. I just needed to know in advance what to get."

Both the Carnivore2 and the MegaFlashROM support disk emulation. The Carnivore2 supports it through Nextor’s EMUFILE, and the MegaFlashROM SCC+ SD supports two ways for it, through Nextor’s EMUFILE and through OPFXSD (the older solution).