Here's what I've found to be the case.
High temperature pros:
Shorter lag time, faster fermentation, quicker flocculation (some yeasts), quicker clearing (some yeasts), sometimes produces estery characters that are desireable but mostly not at higher temperatures.
High temperature cons:
Compromised yeast (higher cell mortality during rehydration and growth phase), production of fusel and other higher alcohols, undesirable estery flavors, undesireable phenolic flavors, slower flocculation, slower clearing, rocket fuel/gas-ahol character, higher production of SO2 and H2S, reduced expression of fruit and spice in melomels and metheglins, yeasty, and solvent like flavors, more suseptible to oxidation.
Low Temperature pros:
Slower more controlled fermentation, better flocculation, more complete and sometimes faster clearing, preservation of varietal honey characters, lowered risk of producing off flavors, better expression of fruit and spice in melomels and metheglins, more volume/mouthfeel in Traditional Meads, off flavors minimized, off aromas minimized, more elegant (structure and complexity) lower alcohol meads, less hot higher alcohol meads, and production of desireable esters (isoamyl acetate, hexyl acetate, phenyl ethyl acetate)
Low Temperature Cons:
Slower out of the gate to begin active fermentation, slower fermentation, stuck fermentation, incomplete fermentations, beneficial ester production, need higer levels of oxygen, subject to competitive wild yeasts due to slower start time, can be difficult to get the fermentation started.
Hope that helps,
Oskaar