[Japo]

If you ask a Spanish speaker the difference between u and w, we'll say no difference. Language scientists classify them differently because w is u when preceding another vowel in the same syllable, thus a "semivowel". Whatever their reasons, the momentary sound is or can be the same.

beta is just b when it happens to be pronounced in between vowels instead of at the start of a word or sentence. Again we make no difference and most Spanish speakers won't realize, it's just that when you're speaking fast you don't stop to shut your lips to make a b. But whether you do, for emphasis or by chance, or not, it's considered the same letter.

There are 23 letters in the Latin alphabet. B and V are the same, as well as C and K (used in foreign words only) or Z depending on what follows. QU is the same as K. H is completely mute (not aspired), so no sound. Spanish has the extra sounds Ñ and CH (tsh), both perfectly distinguishable from any other letter; also LL, but nowadays Spaniards have merged it with the semivowel Y because it was too close so it was no good for us (the same reason why we got rid of aspired H centuries ago).

That means Spanish has only 21 phonems (whatever scientists say about w and beta), and none of them is close to any other. That's why it's so easy to understand. You never need to ask other people to spell a new word, even if you're just learning, whereas in English even native speakers need to do it for any unknown word such as unusual person's names.

Greek happens to have almost exactly the same phonetic system as Spanish, and Basque does too for reason of kinship, despite being completely unrelated philologically.