Snapshot time with reverse incremental can be up to 3x longer.
During the backup, forever incremental, it does 1 seq IO for every write to the incremental file. It is only after the backup is done, and the snapshot is removed that the merge start
Reverse incremental does 3 IO per write during backup. One to read the blocks that needs to be overwritten, one to write that block to the reverse increment and finally, the last IO to write the new block.