In the second brakhah of the amidah, מחיה is vocalized with a segol under the yud in some siddurim--making it a present-tense verb (1); and with a tzere in other siddurim--making it a noun in construct state (2). The choice between noun and verb is also relevant to the the other predicates applied to God in the paragraph (and in the other brakhot of the amidah, and in most brakhot in general), even if they happen to be words for which the two forms are identical. What are the reasons for choosing to take these words as verbs and what are the reasons for choosing to take them as nouns and what sources have discussed the issue?
(1) See the table of גִּזְרַת נָחֵי ל"ה verbs, specifically בניין פִּעֵל in the tense הווה, showing that the second root letter is vocalized segol.
(2) See Gesenius ¶89 2 (c): "Nouns in ־ֶה from verbs ל״ה form their constr. st. in ־ֵה...."