Both packages are for data manipulation, but on surface and internally they are very different.
internal The algorithms in IMD build from scratch for columnnar tables and the way Julia works. Most of these algorithms are home made to fit some criteria that I had in mind and you wouldn’t find them anywhere else.
on surface I mentioned some differences in the announcement, however, those are just few of them. I provided more details of the IMD features in its documentation. I tried to keep the syntax of IMD familiar to DataFrames users but it doesn’t mean IMD uses the same syntax as DataFrames; some places they just use similar name for functions but the syntax is very different, like filter, some places they use similar name with similar syntax but different options, like unique.