Electrics are usually a bit smaller in size. There are a couple of reasons for that. The reasons tell you something about electric.

Nowadays, a couple of mfg's are offering "40 size electrics" etc. They do that to give some sort of size description that most modelers would understand. But when you look closely at the "size" they're talking about the size really is interesting. The electric that is supposed to be say a 40 size really is a 35 size usually. Why?

The batteries nowadays are expensive. And to fly much, you're going to need more than one. And you're going to also need a charger that'll work at the flying field and preferably work quick enough that it's worth lugging to the flying field. And even with expensive batteries those mfg's size their planes on the small side because the electric motors they choose to describe in glowfuel engine sizes aren't powerhouses. They could easily have chosen to do differently, but universally did not. They certainly have more powerful electric motors. But they didn't. Cost might have been the driving force. Because when you look at the really big electrics, costs are so outrageous that they aren't going to scare off the modelers who're shelling out those big bucks and they call a spade a spade.

Look closely at whatever electric you are interested in. Compare it's size and cost with glowfuel models in the same range. Then remember that the electric is going to require a couple of flight batteries, not just one. They're cool airplanes, but nowadays aren't exactly equal. If they're different models the electric is usually smaller and lighter.

But if you convert a gas model to electric you find a different picture. Very often the converted model comes out heavier. And the price of it's batteries is eyeopening. It's interesting that if you compare a "40 size" electric model to a 40size gas, the electric is usually at least 10% smaller and is almost always more lightly constructed and winds up weighing less at flying weight. It'll need less expensive batteries, but also won't handle wind as well. But convert a 40size gas design to electric and the result will be a measurably heavier ready to fly airplane that set you back a months pay for engine and batteries.

Both work well. But pay attention to the details and whichever suits you won't disappoint you.