You're right, not all inversion tables are created equal. I did lots of research before I bought my table and IMHO the safest table is the Teeter Hang Ups, by far! Not discounting what others say, we all have to purchase the one we feel safest with due to the fact we're hanging upside down lol!
The Teeter tables are more expensive than others but for me, price doesn't matter when it comes to safety. You can check out the Teeter at HSN, they have a monthly payment schedule where you can give your credit or debit card number and they'll charge it once a month until it's paid for, no extra charge. Lots of people take advantage of this option to be able to have a GREAT/SAFE inversion table.