This is just what I do, but if you are going to make a park with just one specific scenery type then use a smaller size park, but if you are going to make a park with different types of scenery go for a bigger park. If you think differently please reply.

Mine are always 50x50 regardless of the scenery.

Thats not true Rick, you've made a few slightly bigger ones I think.

I agree with you, RCTycoon14. I mean my last park was only a 75x75, but I had to chop it up into 3 different sections to finish it.

My last park was 85x85 but with some land outside the gate. It uses only one main style of scenery but since this was a scenario for people to build more, I felt the larger space was needed.
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It depends how many ideas you have for a park and how much time and space you need. For example if you want a large lake in your park you need a bigger park map so you still have space for rides. For a design mini park I'll use a 50x50, for a bigger resort park maybe 100x100 or 128x128. I find I tend to run out of rides for bigger maps than this before they're full

I should clarify. I've never made a solo park larger than 50x50 by choice. I've made some larger for contests but that was because the scenario was provided to me and I couldn't change the size.

I've said it before and I'll say it again...it ain't the size that counts...it's how you use it!

I guess what it really is, the smaller the park the easier it is to theme because there isn't too much space to fill in.

I'd say that if you've just started playing then you should start small so you can get the hang of filling up an area with one theme. Then as you get better and you learn how to manage your themes you can make the map bigger.

Same as ^ said.