I've had the pro tools 105 and the HB302. Both are good benders.
The 105, as a manual bender, is a workout and requires a fixed mount to something like the floor or a receiver hitch (though slop in a hitch mount makes for some accuracy challenges when bending multiple or compound angles). The 105 can also be converted to air over hydraulic which makes bending easier. The disadvantage to the 105 is that you need to reset the pin on the die every 20 or so degrees (forget the exact increment) which can cause the tubing to slip in the die if you're not careful which can cause a single bend to be in multiple planes and not lay flat on the ground. It's advantage is it can bend beyond 180-degrees which is useful if you plan to make hoops (like a shock hoop or driveshaft hoop). The 105 has a friction/guide block (considered a consumable by me) that slides along the tubing which essentially pushes the tubing around the die. The disadvantage of benders like the 105 is the guide block can become damaged and gal the tubing (scratches, gouges, etc). The only fix is to replace the guide block.
The 302 is also called the one shot because it allows a single bend, up to maybe 120-degrees, without needing to reset a pin. Unlike the 105, the 302 doesn't use a guide block and is a frictionless bender which uses the die to roll the tubing off of the follower. Because the design is frictionless, this style of bender is suited to bend aluminum and other soft metals which the 105 would destroy or mangle. Because of the follower, the 302 requires a table like surface for it to rest on and the follower prevents the operator from sequencing bends right after each other as easily as the 105 because of the table top surface. Between the two I found the 302 to be superior in many ways and bends were much more repeatable.
Most cages are made from 1 3/4 tubing and use HREW (electric weld tubing that has a seam down the inside) or DOM (Drawn Over Mandrel to eliminate the seam). 1 1/2-inch tube is a little small. The min recommended diameter (I strongly recommend sticking to the NHRA requirements as a guideline) is 1 5/8 x .120 wall however, though it can be found, it's uncommon and is typically expensive as a result. It's preferred for internal cages where space is at a premium or where weight is a concern. That being said, go for 1 3/4. HREW, because of how it's formed has a less constant wall thickness and, as a result, can flatten as you bend it, possibly split at the seam, and can be more difficult to perform repeat bends. DOM, on the other hand, has a much more consistent wall thickness and, as a result, can be much easier to get good results. In either case you'll want some type of angle finder on the bender to help you figure out where you are. There are some home made versions if you want to save a buck.
I still have my 302 which I used professionally for years and has thousands of bends on it however I use it much less often now-a-days. Most that buy them build a cage or two and then store it away until they get tired of looking at it and put it up for sale. In my area (Denver), there's almost always a bender on Craigslist. Maybe look in your area and save a buck.
