Irish vs Welsh conservatism

[Znex]

Welsh and Irish are subject to a lot of similar sound changes regarding loss of final syllables, intervocalic lenition, etc. Irish has managed to hold on to more nominal and verbal morphology, but the magnitude of the sound changes isn't that different.

Even that's arguable, depending on which varieties you look at. Written Irish retains the genitive but in spoken dialects it's often restricted to fossilised forms. Welsh analytic verbal paradigms tend to retain distinct forms for each person-number combination where Irish paradigms are more analytic. For instance, compare the preterite inflections for "speak" in the colloquial standards of each language:

Welsh
siarades i
siaradest ti
siaradodd e/o/hi
siaradon ni
siaradoch chi
siaradon nhw

Irish
labhair mé
labhair tú
labhair sé/sí
labhraíomar
labhair sibh
labhraíodar

(Connemara dialect--arguable the most vigourous of the traditional spoken varieties--takes this even further, replacing labhraíomar with labhair muid and labhraíodar with labhair siad. Conversely, some NW Welsh varieties replace the entire analytic preterite with ddaru + pron + VN, i.e. ddaru fi siarad, ddaru di siarad, etc.)

I think it's Scottish Gaelic that goes even further and has a single form regardless of person and number (although at the same time, it retains conjunct verbforms), and even a frequently-used periphrastic present tense reminiscent of the Welsh present tense (however the Welsh auxiliary verb/copula conjugates, while the SG auxiliary verb/copula doesn't).

Scottish Gaelic
(future tense)
Labhairidh mi
Labhairidh thù
Labhairidh e/i
Labhairidh sinn
Labhairidh sibh
Labhairidh iad
(present tense)
Tha mi a' labhairt
Tha thù a' labhairt
etc.

Welsh
(synthetic future tense)
Siarada i
Siaradi di
Siaradith e/o/hi
Siaradwn ni
Siaradwch chi
Siaradan nhw
(periphrastic future tense)
Bydda i'n siarad
Byddi di'n siarad
Bydd e/o/hi'n siarad
Byddwn ni'n siarad
Byddwch chi'n siarad
Byddan nhw'n siarad
(present tense)
Dw i'n siarad
Rwyt ti'n siarad
Mae e/o/hi'n siarad
Dyn ni'n siarad
Dych chi'n siarad
Maen nhw'n siarad