Apart from the price tag, the biggest difference is that Links lets you customize virtually every aspect of your interface and add third party modifications.

On a more subtle note, HyperSeek simply doesn't work (leastwise it didn't two months ago) -- it's auto-installed and linked to the HyperSeek folks' server in some fashion in the trial version. We gave up on it after two days of trying to get it to work and getting no response.

Links doesn't gurarantee any support for the trial version but has a huge community of peer support. I haven't been able to get answers to any of my questions, but I suspect it's because I didn't post them well, or it's assumed I didn't read the README and faq <g>.

My bet is with Links, or the pay version of IndexFinger.