Not just pistols, but gas guns in general require significantly more routine maintenance and cleaning, and are also much more prone to breakdowns and performance issues (especially GBB pistols). They're also affected greatly by the ambient temperature.
Whereas an AEG is only mildly affected by temperature, most notably shorter battery life, which can be avoided by using LiPo batteries. Although some AEG's break down fairly quickly stock, most AEG's given some basic upgrade parts have pretty good track records. Fully upgraded AEG's like the ones I do don't break down for a minimum of 2 years, and that's with zero maintenance and zero cleaning.
Across a broad spectrum of playing conditions (throughout a whole season), and especially since newer players generally don't know how to take care of their stuff, AEG's are your best bet.