Also, doing spec will make methods a lot easier
You'll pretty much be set for the calculus and trigonometry parts of methods by doing spec alone. Apart from a couple of other little things, it's just the probability that will be new ground for you
I hardly did any work for methods this year, but I did a fair bit for spesh, yet I still managed to perform really well in methods regardless
For me, doing spec made methods ridiculously easier, to the point where I didn't have to study for it much at all (That's how I felt - it may not be how others feel about it)
If you're set on devoting most of your time to just one of the two subjects - if I were in your position - I would choose spec, simply because working for spec alone will allow me to score well on methods to some extent
But yeah like the others have said, it would be best for you to set aside an appropriate amount of time for your methods revision as well, and it's not like you'll be pressed for time. If you organise the year well, you will have more than enough time to study