The flavors are similar. Rye Malt has gone through the malting process and can convert itself in a mash. Flaked rye is more like coarse oatmeal and requires 2-row for conversion. They are both sticky.
I would just add that the flaked rye has been gelatinized and that makes the starches readily available for conversion to sugar. You need to mash it with some 2 row to get that conversion, simply steeping it by itself won't work.