looking to buy a new one

The first question is whether you bought the SGX because you are short-waisted or your height is less than 5'6"

If you are taller, the MGX will give you an additional 1/2' of penetration, and might provide increased prostate contact. It has the same lower stem as the SGX so the principles of operation, anal contractions, will remain the same. I find the MGX a bit 'bulkier' in the lower canal and get good Cowpers contact from it when I compare it with SGX or Helix.

Helix on the other hand is bulkier in the upper body and its lower stem (base) slides through the anus so it's more self-adjusting with regard to prostate contact. I get far less Cowpers contact from Helix but, clean and well lubed it's more agile from my breathing and subtle pelvic muscle contractions. Once mastered it takes off much faster than either of the older models.

You may find Helix more sensitive to body position and have to change your preferences with regard to being on your side, back or stomach. When I used it during couples sex a spooning position worked great! ...hth...

i didnt get the sgx for this reason but i am 5'5

I'm only an inch taller than you and I find the Helix works well.

If you intend lying on your back while using it I would suggest you cut off the curly part of the handle. Make sure you smooth off the but end so that there are no sharp edges.