It's again about my own experience, i.e. about apartments up to Euro 50/day. And don't forget there are always exceptions.

1. Availability of your hosts. Normally your hosts will live not far from the apartment you rent, so you'll be able to get any help promptly. Foreign hosts are ready to help, too, but they often are in their country when needed, and in this case it may take some time...

2. Parking. My experience is that if the apartment description includes "free parking", your Spanish hosts will have an underground parking in the same building (some times in another one, but very close to where you live). This is generally convenient, and your won't have to get into a hot car. If Russian people mention "free parking", this often means that you can find a parking place in the streets around, but it may take some time and the car will always be hot.

3. The neighborhood. An apartment from Spanish people will normally be in a regular Spanish house. There will be Spanish people living next door and Spanish children playing in the yard. If you want to "immerse" into Spanish life and practice the language, this is apparently an ideal environment.

See also "3 reasons to rent an apartment in Spain from Russians".