上に|うえに

Adds a further fact on top of one already stated, meaning 'on top of', 'besides' or 'not only… but also'. Both facts usually point the same way, either both good or both bad.

Used in both speech and writing to pile up reasons or characteristics. The second clause often contains も (料理もおいしい), and the added fact typically strengthens the overall evaluation. 上に attaches directly to a predicate to join two clauses, whereas その上 is a standalone conjunction placed after a completed clause or sentence (安くて、その上、おいしい).

• に加えてN3「に加えて」usually attaches to nouns; verbs and い-adjectives take 「の／こと」, and な-adjectives can take 「である（こと）」. It leans written/formal and often pairs with 「も」, whereas 「上に」 is also common in speech and requires matching polarity before and after.
• だけでなくN3「だけでなく」 also expresses addition and is often interchangeable with 「上に」 when both sides point the same direction. However, it can combine one positive and one negative item, can be followed by requests or invitations at the end, attaches directly to nouns, and sounds slightly more casual than 「上に」.
• ばかりかN3「ばかりか」 also means 'not only... but also...', but it emphasizes that B goes further than A or is unexpected, with a stronger, more written tone; the latter clause often pairs with も・まで・さえ. It attaches directly to nouns, while 「上に」 needs 「の／である」.
• のみならずN2「のみならず」 also expresses addition but is formal written language; it can attach directly to nouns (e.g. 「語学のみならず」) and can start a sentence meaning 'not only that'. 「上に」 is neutral in register and requires 「の／である」 after nouns.
• その上N2「その上」 is a conjunctive adverb used after a sentence or after 「で／くて／て形」 forms, while 「上に」 attaches to the plain form of verbs and adjectives or to 「な／の／である」. Both add same-direction information, so 「安い上に」 can be rewritten as 「安くて、その上」.
• はもとよりN2「はもとより」 attaches only to nouns: it first presents the obvious A, then extends to the further B, often with 「も」 or 「まで」 in the following clause, in a written style. 「上に」 can attach to verbs, adjectives, and nouns, and simply stacks two same-direction facts.

Unlike に加えて (mainly after nouns and more formal) and the broadly neutral だけでなく, 上に emphasizes stacking same-direction facts. ばかりか and のみならず add surprise or emphasis, with のみならず the most literary. その上 is an independent conjunction that follows a finished clause or sentence rather than attaching to a predicate, and はもとより treats the first item as obvious ('let alone').