Unlike the Sixtyclone, the Ultimate 64 replaces the chips as well as the circuit board. If you just want a brand new, guaranteed to work replacement motherboard, Sixtyclone is the way to go.
Why Ultimate 64 rather than BMC64 Raspberry Pi emulation, The C64, or MiSTer FPGA?
Though the emulation on the Raspberry Pi is way cheaper, and MiSTer FPGA is also cycle-accurate, what the Pi or MiSTer can not replace is the complete hardware compatibility – the Ultimate 64 allows you to use actual 1541 floppy drives, tapes, and cartridges as if you are using an original C64.
You can even develop hardware for the C64 on the U64 with the use of a user port adapter.
The Ultimate 64, as well as replicating the base Commodore 64, allows you to run at faster speeds, with more memory, emulating REU and accelerators.
As with TheC64, you have modern conveniences such as the ability to use a HD HDMI flat screen tv (both NTSC and PAL), use regular DC adapter, and USB disk (including exFAT allowing maximum disk size of 2TB!)
Unlike TheC64, however, the U64 also has analog/S-Video option, incorporates Wifi, an Ethernet port, and for chip music aficionados, sockets to use two original SID chips, as well as the pair of FPGA recreated 8580/6581 SIDs.
In addition, the U64 builds upon Gideon’s older Ultimate-II+ product, which provides emulation of Commodore 1541 drives.
Ultimate 64 Video Overview and C64 Game Testing
While it is priced in a way that puts it out of reach of many (€ 177,69 in my case), it really is the Ultimate 64. Currently it seems only the more expensive Elite version is available which adds a couple of nice things such as Zif sockets.
Get more information and pre-order at ultimate64.com