I believe it is a matter of personal preference. All the gates will do essentially the same thing; contain your dog while you are out. I believe crating is better as long as you get a comfy crate bed and give them a long walk before leaving. That is my opinion, and other people will say the pen gives more room. Currently I use a pen for the Yorkie I'm having a trial session with because I don't want to spend $65 ($50 for crate and $15 for bed) on a crate if I won't keep it. I had a pen from my rabbit.
If you decide to go with the pen, I think the Precision ones coated with black look the best. Be sure to have toys, food, water, and pee pads in the exercise pen (if you leave for long times in the day). If you have the time it is probably best to crate train her for now because she probably won't be potty trained when you get her.
Let's see.. must haves.. here goes! Crate or exercise pen, pee pads, toys, food, food/water bowls (stainless steel or ceramic), place mat?, a few beds, toys, harness, leash, ID tags, toys, treats, and don't forget the toys!! Hehe
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Vanessa