Still, I guess I'll go ahead and make my recommendation. If we're talking about being on a budget, then the good old happy time engine and kit wins hands down.
They are so inexpensive that I don't even count the cost. I've regarded my bikes as virtually free. Not quite accurate, I know. It costs a couple of hundred bucks. But compared to the cost of any other motor vehicle that is competent to get you around the neighborhood and a bit further, nothing comes close to this price.
There is a bit of a learning curve with them. Learning how to keep them operating without frustrating you every day. Not all that hard, but it's something that needs to be dealt with. You gotta learn to ride them, too. You can beat the bike to death and it'll return the favor. You gotta learn to roll with the punches. But that's not all that hard either.
And I'll bet this is all true of other, more pricey, options.
So I vote for the happy time.