Sigma did a great job in creating the 70mm macro. It's focal length is excellent when you're using a non full frame camera as it becomes a 112mm. The Canon 60mm macro is the closest to being a 100mm on a non full frame camera. The disadvantage is that it is an efs lens which means you cannot use it with full frame bodies. The 70mm served me well till I got my 5d mk2.
For a full frame camera, the 70mm is a bit short. It does not give me enough working distance from subject to the tip of my lens, especially with the Canon macro flash installed, or a hood. I usually freak out bugs because I am way too close to them when I take macro shots...so instead of getting the shots, bugs usually would fly away. Using it as a general purpose lens was fine. Though the autofocus was whiny and it was way too slow even when you switch your focus to the non full focus mode. I needed something that would allow me better working distance for macro shots as well as a general purpose lens that focuses quickly.
The best replacement for my 70mm in my opinion is the Canon 100mm macro. It's a pretty well made macro lens that doesn't break the bank. They usually fetch around $550.00 brand new and around $400-$450 used. I browsed online for the best deal and I was able to get one for $409.00 used.
3 days later I got it. No box, no instructions, only the lens. The lens though was perfect...no scratches, the glass was clean. It was pretty well taken care of. No signs of use whatsoever. So I slapped on a uv filter and slapped it in my camera. Here are the best features of this lens:
Very well constructed. Metal mount, plastic barrel although feels very well made for a mid range Canon lens.
Focus limiter switch works pretty well for macro or general use.
USM motor gives the lens fast silent focusing especially for general use.
Gives you around 6 inches of 1:1 ratio distance from the tip of the lens to your subject.
Focus ring is pretty wide. Feels well dampened but not too tight.
It does not extend when focusing. Very important for a macro lens.
Closes down to f32.
Sharpness is unbelievable. Though most macro lenses are built sharp.
The color rendition is superb.
Usm motor allows you to tweak your focus after it has locked without switching between manual and auto focus. It does not rotate either during focusing. It also maintains it's original size even when you're into the 1:1 magnification, this prevents you from accidentally bumping your lens into your subject or the surroundings...although the 6 inches of minimum focus is enough not to let you bump your lens into whatever you're taking pictures of. The auto focus is so fast it's even useful for macro. I have tried this and the autofocus seems to pick up really close subjects too. The minimum f32 aperture is also very useful for macro photography if you need it.
The thing that I didn't like about this lens is when you use filters like a uv filter, that it does not allow you to attach the Canon macro ring light directly to it. You would have to remove the filters first before you can attach the ring light. I would rather keep the filter in there to protect the lens even if it's a pain to remove it every time I attach the ring light. The only way around it is to attach an adapter to your filter which will allow you to attach the ring light adapter into the adapter that you just installed. In that case, there will be 3 attachments into your lens...the filter, the adapter and the ring light adapter. Pretty complicated huh?
Though it has a bit of shortcomings like the ring light issue and the lens hood not included issue, I still do love this lens. I still would buy another one if mine broke. I bought an aftermarket lens hood for it because they are cheap. I rarely use it though. Compared to my 70mm, they are pretty even in sharpness. The big difference I saw was the contrast and the color rendition of this lens. Most of my sample shots were not color corrected in lightroom. Shots usually are good straight from the camera.
For full frame cameras, this lens is excellent both for macro and general use. For aps-c cameras, this is still pretty awesome for macro shots, not too useful as a walk around lens though as it becomes a 160mm lens. For me, it's one of the best lenses ever made.