Neither one sounds right to me. Why does the concept of coming attended or unattended even enter into this? What's the context? What's the significance or purpose of coming alone?

Do you mean "Why don't you (come and) see for yourself?". :)

I need your help, guys

Which one is more common: 1) why don't you come and see by your own, or 2) why don't you come and see on your own?

Hi Alex, to answer your question, the most common way to say this in English is: "Why don't you come see for yourself?" I hope this helps. Díme si tengas más preguntas =)