Oromo and Somali are much less similar than German and Scandinavian languages are. I can assure you that at least. I can get the gist of a Scandinavian text, but Oromo text is a mystery to me.
It’s not that the 2 languages are “much lesser”. They are very similar if you understand both languages. It’s that some words within each language are slightly pronounced differently. If a Somali were to try and learn Afaan Oromo, the easiest dialects they’d choose are the eastern(hararge) and Borana/ Garre dialects. There are a lot of similarities once you dig deeper.
I found this online a while ago, kind of interesting how similar the numbers are within all these Cushitic languages..
Proto-HEC+ *mitto *lamo *sase *shoole *omute *leho *lamala *saddzee *honso *ton-me
Burji micca, lama, fadi, foola, umutta, lia, lamala, hiditta, womfa, tanna
Gedeo mitte, lame, sase, shoole, onde, jaane, torbaane, saddeeta, sallane, tomme
Hadiyya mato, lamo, saso, sooro, onto, loho, lamara, sadeento, honso, tommo
Kambata matu, lamu, sasu, shoolo, onto, leho, lamala, hezzetto, honso, torduma
Sidamo mitte, lame, sase, shoole, onte, leye, lamala, sette, honse, tonne
Yaaku wehe, c'e, xaat, çwen, xoopi, ilé, tisíbo', siite', saakal, qapon
Birale akala lama zéha talaxa hobbe s'anafa taxanke íísta gólanke coma
Tsamay dóokko lakkí zeeħ sálaħ xóobin tábben táħħan sézzen góllan kúŋko
Afar iník-i nammáy-a sidóx-u firéy-i konóy-u lixéy-i malxíin-i ba-xáar-a sa-gáal-a tában-a
Saho iniik lammaa adoh afaar koon leeh maleheen bahaar sagaal tammon
Dasenech tákac naama seddi ?affur cen li tiyya síét saal tommon
Elmolo+ t'óko l'ááma séépe láfur kên yíi tíípa fúe sáákal t'ómon
Arbore tokkó laamá seezzé ?afúr čénn ĝih tuzba suyé saagald tommon:d
Bayso 'ko: 'lama 'sele '?afar 'ken 'le todo'ba si'd:e 'sa:gar 'tomo
Rendille kôw l'áma s'éyyaħ 'áfar cán liħ teeb'á sitt'êt saag'ál tom'ón
Somali kow, laba, sadeh, afar, shan, leh, todoba, sideed, sagal, toban
Tunni ków lámma síddi? áfar šán lí? toddóbo síyéed sagáal tómon
Aweer (Boni) kôw lôw síddè áfar shâŋ líh didd'óú siyy'êd s'áágal tam'án
Oromo tokko/takka lama sadii afur shan ja’ah torba saddeet sagal kudan
Borana toko lama sadi afur shian jaa torba sadeti sagal kudan
Gidole (Dirasha) shokku lak(ki) halpatt afur hen leh tapp lakkushet hund'a
Bussa (Muusiye) shukk'uha taammu halpatta afurii henii lehi seppa saatteti hund'a
Konso takki lakki sessa afur ken lehi tappa sette sakal kud`an