I asked a questions for which usually i find an answer myself.
After i read this article i found out as follows comparing Raiblock with IOTA
IOTA has a “Cooridinator” which is temporarly placed to secure the network untill it is scaled up eough
RaiBlocks has a “representative system” which will be there forever and it is basically
an address with a lot of money. The expetise says:
The only area where I see a slight issue is in that of their representative system.
This is a potential attack vector
IOTA has a unique feature Off-chain Transactions
RaiBlocks The sender must be online to make a transaktion
IOTA has a mechanism to trim ledger size in a process called snapshotting
RaiBlocks does mot, and over time, size will definitely become an issue
IOTA is the WINNER