I have two sources for the Shanghainese pronunciation of "無" (leaving colloquial pronunciation aside); one says the initial is /v/ while the other /ɦ/. I found the same differences in some characters like "武" and "巫". Why is that? Is it just a regional difference?
1, 吳語學堂, not 吳語學當
2, 吳語小字典 offers the romanization form. 吳語學堂 offers IPA. You can't directly compare the two. You need to click the link on the sidebar of 吳語小字典 to see which symbol represent which sound in its romanization system. (However, even that link does not provide IPA, so you have to know Wu first to fully understand its romanization system.)