I'm looking for a saw to complete my fencing project. I was using a circular saw to cut the fence rails but it went for a walk, if you know what I mean.

I'm now wondering if a jigsaw would be a worth getting instead of another circular saw because I have more uses around the house for a jigsaw than a circular saw. However right now I need the saw to cut fence rails in half so I can finish my fence. These are 50x100mm SG8 KD treated pine and possibly laminated fence posts (112x112mm), although its fine if it can't do the posts.

I have found a number of jigsaws that claim to cut up to 80mm and one, a bosch, even up to 140mm. I need the cuts to be flush and straight so my primary concern at is that the jigsaw blade will flex giving an uneven cut across my wood.

In saying that I have read the jigsaws can give really straight accurate cuts even in this wood or I'm a little confused.

Buy choosing a good quality saw and the right blade can I use a jigsaw for this purpose with results similar to that of a circular saw or even a mitre saw?

What should I be looking for in a jigsaw to meet my needs? or can I simply not use a jigsaw for this purpose?