One problem for many machine users is training in the same grove/tract without sufficient variation -- over time this leads to injury; one solution is to mix-up ones training periodically. Some machine manufacturers have also found ways to prevent a lot of this (both Body-Solid & Inspire make models that allow for a lot of free-motion exercises rather than all just fixed-tract exercises).
Some machines are engineered/designed better than others & each design has an affect on the resistance felt at any given point.
I like many types of exercise apparatus -- I even make my own when I can't find what I want (as a matter of fact, this morning I just completed modifying a Body-Solid Triceps Chair to double as a Biceps Chair for dumbell & some machine-cable work -- it's sweet). There's a lot of hokey contraptions out there, & a few good ones as well (this statement is especially true for abdominal-training contraptions). Buyer beware -- & it's best to be able to try out an exercise doo-dad before you buy it (as often sales-pitches are just unfounded hype).
With free-weights you may get what you pay for, but sometimes you can get the stuff on sale (or slightly used & quite inexpensive). Sears (formerly Sears & Roebucks) & even JC Penny used to sell inexpensive, plastic-coated starter weight sets of about 120-125# for about as many bucks (barbell & dumbell kits). If you go this route, then consider that you may need to purchase some extra collars (as they always seemed a few short) & some extra plates (some very-light ones for progressive-resistance training & some heavy-ones for heavier exercises &/or for when your strength increases); of course, if you can afford it, you can get some York weights (or a brand of that ilk) & have 'em for life as such are high-quality, durable weights (unlike the plastic-covered plaster weights which eventually crack).
Also, there's a lot of free or near-free training-aids all around; things like a couple of sturdy chairs for doing parallel-bar dips, or step-ladders, stair-cases, &/or sturdy benches for doing step-ups (with or without weights). If you've got a good imagination & an eye for safety, then you'll find many ways of improvising/adapting & saving bucks.