The Eastern and Western Roman armies were about an even match, with their fair share of victories (Alaric in 402, the 397 Huns, Uldin, Catalaunian Plains,
If one looks at a map of the Roman Empire, one sees its most vulnerable points are the Balkans, Syria, Gaul (especially, given high population density, closeness to more populous barbarians, and weaker military presence, Southern Gaul). Its least vulnerable points are Tunisia (conquered by the Vandals in the 430s, reconquered by the Eastern Romans in 533, conquered by the Arabs in the late seventh century), Britain and Armorica (abandoned by the Romans under Constantine III), South Italy, including Sicily and Sardinia (lost to the Romans over the course of the sixth through tenth centuries), Portugal (lost to the Sueves and Visigoths over the fifth century), and Southern Greece.
It’s worth pointing out all the peoples who had a hand in destroying the Roman Empire (Turks, Goths, Arabs, etc.) were some variety of seminomadic barbarian.