Ok, so I'm not new to this whole online "dating" thing. Sounds kind of pathetic/scary, but I've been meeting people from the internet since I was 16...
A little over a year ago, I was a paying member of eHarmony, and I had no success. I kept up with e-mails from my so-called matches, and when it came time to move past e-mails, the matches these "experts" found for me decided that we weren't compatible. I have gotten the same results from a free website: PlentyOfFish.com.
In my opinion, I think paying for a dating website is a waste of money.

Although I haven't tried either site -- I met my husband online BEFORE either site started! -- here's some helpful advice for which dating site to choose.

1. Think of dating sites like shoes. Sometimes you need a great running shoe, other times a sexy stiletto. There is no ONE perfect shoe, or dating site, for everyone.

2. Know thyself. Your friend may rave about sailing, but if you get seasick, that activity isn't for you. Stick with what YOU like.

3. How do you figure out what you like? Browse the sites. Many will let you browse for free and/or offer trial periods.

4. Start with two sites -- one of the majors, like Match or eHarmony that you mentioned, that have the most members and a smaller speciality site for fun. There are online dating sites for every passion -- animal lovers, wine drinkers, tennis players, yoga enthusiasts, etc.

5. Set a time limit. If you don't have success after x weeks, move on to another site, create a new screen name, submit a new ad and picture. With over 1000 online dating sites, the world is your oyster.

Above all -- have fun!