You're right that there are two pronunciations of 'with'. The final 'th' sound can be pronounced either as a voiced consonant (like the initial sound in 'the' or the final sound in the verb 'breathe') or with an unvoiced consonant (like the first sound in 'thin' or the final sound in the noun 'breath'). What's interesting is that the majority of native speakers are unaware that there are two pronunciations. Most of us just say 'with' with whatever final consonant we grew up using and don't notice that other people use a different one. In answer to your question, you can use either. It really doesn't matter. Use the one which you feel most comfortable with. Here's a discussion we had a few years ago on this question: https://www.italki.com/post/discussion-195994

It might be better to do an audio so we can hear how you think it’s pronounced. Because I’ve never heard any more than one way to pronounce it.

Hi Lin! How are you doing? Please find below two acceptable pronunciations. 1)wɪð/ (sounds like "width") 2) / wɪθ/ - Famous Song - "With or Without you" I hope this helps. Keep up the good work!

The difference between the two versions of "th" is so nuanced that as long as you say a real "th" (with enough air), you should sound just fine saying "with." I'm not sure you're going to get a good answer on a written forum. You need to find a native speaker who can listen to you and correct you if you're saying it wrong.

I don't want to confuse matters, but in London you might hear a /v/ at the end.