Dress Forms

I actually have some strong opinions on dress forms, particularly the lower-end varieties.  Besides being a professional tool, a dress form says a lot about the seamstress displaying their work on them. No dress form will truly be your body twin, but if you learn how to use a professional form properly

Adjustable Form

you'll achieve the best results.

Adjustable Forms.  When I see a gown on an adjustable form I know the seamstress hasn't invested seriously in her profession - she is probably a hobbyist working on projects for her family and friends. Professionally, this is not a good investment. They are flimsy, their plastic dials will fail, their adjustment options are awkward (Large bust? Congratulations you win a larger underbust, too!) and there are no proper indications of key design points (bust apex, shoulder seam, nape, dart placement, etc).  Not to mention those dials are going to get in the way of some critical places you'll want to pin like the waist, underarm, and high hip - I'd add low hip but the dress form doesn't seem to go down that far, does it?

Foam Form

Foam Forms.  My first dress form (in college) was a Uniquely You dress form.  It's a molded foam shape that has a separate cover that you fit to your body and then back over the form (very snug fit).  It's been surprisingly durable and held up for 20 years so far.  It's squishiness is especially useful for my historical projects when I need a corseted shape. My only complaint is the stand, which I've since upgraded to a rolling one.  If you're working with a limited budget, this is what I would choose over the adjustable model.  It's ideal whether you're sewing for an individual and want a perfect match, or doing general sewing for others in which case you can pad it out like a professional form (as described below).

Pro Form

Professional Forms - typically with collapsible shoulders. Most people are turned off by the price and the fact they are one fixed size. But once you learn how to pad out a dress form for a custom fit like a pro you'll never go back. You can use layers of batting, felt - whatever works - and build it out to your client's shape.  These forms are designed to last for years of heavy use.  The seams in the fabric covers are usually well placed for identifying shoulder seams, breast apex, natural waist and other key measuring points.

Craftsy.com has a class on how to Customize Your Dress Form the professional way that I recommend if you want to get the most out of your dress form.  She's a bit kinder when she addresses the adjustable forms, but you'll realize how much more work is involved to bring them up to par.