I really have no idea what map is better for Slovenia, TomTom or the "local" map made by Monolit (?). That one is AFAIK not renewed that often but I do believe has a bigger size so could/or should be more detailed (or have more roads in countryside).
I think the last one I saw is 2012 or 2013 and is +/- 34,5 MB in size (compare with HERE 9MB, TT is 15MB).
Someone might provide it (or newer) when you ask nicely. I am no collector and most of times only download what I need myself.