text link are definitely better
you can put some keywords in links and spiders can see that links.
for example pay attention to the phpbb SEO copy right. that links are in text form
and contain two keyword, "phpbb" and "SEO"
when spiders crawl other site that are linked to phpbb seo, and find that links. they can see that two words (i mean "phpbb" and "seo" words) and they can understand that there is relation between destination of that links and that two word.
but images are not contain any word and bots can see the text in image.
"a famous example that can show the importance of the keyword in text links"
late in 2003 many bloggers linked to george bush biography at (-http://www.whitehouse.gov/president/gwbbio.html) by putting two word in links (miserable falure). when people searched for the term miserable failure
in google, the first link in result page is george bosh biography at (-http://www.whitehouse.gov/president/gwbbio.html)
. This was done by a small group of people using links in blog pages.Despite the fact that this page contains neither the word miserable, nor the word failure, and certainly not the term miserable failure, a few dozen links with the words miserable failure in the link text were enough to trick Google.
and another one: when you search word liar
in google. the first link in result page is tony blair biography at (-http://www.number-10.gov.uk/output/Page4.asp). that page doesn't contain word liar too.
when you put some keyword in the text, google will pay attention to them and if you try hard and make many link to your site you can grab that keywords for your site.
im not pro in SEO matters
dcz can explain it more for you