I have to admit I haven't tried all the cutting machines on the market, who can afford that? But I have tried many of them. Of them all, the ones I've kept are the Sizzix Big Shot Pro, the Cuttlebug and the Sidekick and I'll tell you why:
Cuttlebug - I've had my Cuttlebug for so long I can't even remember when I bought it
and it's still a workhorse - always ready to cut, the cutting pads are
still available and it only takes a second to pull it out, make a cut
and put it back. Most of the steel rule dies that I purchased to use with it are up
for sale due to the arrival of my Silhouette Cameo but you can cut any die on the market that is less than 6" wide if you have the proper cutting pads. Length doesn't matter because 12" long cutting pads can be purchased. So, if you don't plan to cut a die that is 6" or wider, this could be the machine for you.
The Sidekick is a tiny machine that works really well for the thin dies. It will take dies that are less than 2.75" inches and again, length doesn't matter because 12" cutting pads are available. I use this for my Cuttlebug alphabet dies.
I purchased the Big Shot Pro because with the proper cutting pads, it cuts every die I own and it has the Grand Calibur's capability of cutting many large dies at once. I realize the Big Shot Pro is expensive but when you add the price of all the smaller die cut machines you could buy for each type of die you cut, it kind of evens out and I like knowing that any die that comes on the market, I can cut. Every once in a while I see a good deal on it and it's so well made I don't think it will ever break. The downside: it's huge and heavy so it needs a permanent place, it's hard to move. I do love my Big Shot Pro.
There are other die cut machines on the market, I think Accucut has one and I know Tim Holtz has the Vagabond. I haven't tested either of them, I'm really happy with the three I have.