It depends on the scope of landscaping - "light duty landscaping" if planting trees/shrubs, and doing some general excavating, or building stone walls a small TLB is more versatile as you can dig holes/trench, then move rock, unload trees, move dirt with a TLB over some distance with one machine. The small TLB's like the used Kubota
B26 or
L39 or JD 110 will probably be the same price range as a 10,000Lb class used excavator.
If you are doing more extensive hardscape with stone, trench work, or commercial site work with things like drain tiles, septic lines/fields then a small excavator along with your skid steer would be better.
if for most jobs you envision you need the skid steer and excavator on site then will they both fit on your trailer? Otherwise its multiple trips, and load unload - not a big deal if you are going to be on site for a few days/week each.
Then as MBTRAC said, the tracks/maintenance on the excavator are a maintenance item more so than a TLB.