The first thing you need to consider is the actual space where you're going to put it. Compact electric ovens usually measure around 45-50 cm wide, so if you have a corner or gap between furniture that already saves you a ton. Before buying, measure the area where you're planning to install it properly, including depth and height. Also check the ventilation requirements, because they need some free space around them to avoid overheating. If you're really tight on space, large toaster ovens (like those Chef-style models or similar brands) can be a decent alternative: they take up less room than a conventional oven, heat pretty well and let you use your kitchen space more flexibly.
About capacity, it's true that compact ones give you less performance than a traditional oven, but honestly for a small apartment you almost never need to fit four pizzas at once. Models with around 25-35 liters will work perfectly fine for everyday use: roast chicken, vegetables, pies, that kind of thing. Look at brands that sell well here like Electrolux, Ariston or even some supermarket brands that have good value for money. What matters is that the temperature control is decent (allowing gradual adjustment, not just two or three fixed positions) and that the heating elements are distributed well so it doesn't burn the edges while the center stays raw.
One thing a lot of people forget: before you buy it, talk to your electrician or check what circuit you're going to use, because some small apartments in Buenos Aires run a bit short on electrical load. If you plug in an oven with 2000-2500 watts along with other appliances, you might blow everything.