I was a certified Sikkens contractor and fanboy for a very long time, until they ended the program several years ago. the Sikkens (now Proluxe) Log and Siding finish is one of the finest, longest lasting paint products I've ever seen. it is also one of the most expensive. I think the best I could do was over $80 per gallon when I priced it last summer, although I have not used this product in over ten years. If money is no object, this is probably the best option. Still, proper preparation of the existing substrate is THE most important part of any exterior painting project, and whatever product you put on your house, know that it is only as good as the preparation.
I know for a fact that some of Sikkens products now being sold under the Proluxe name brand are NOT the same quality as they were when Sikkens was selling their own products. I'm not sure if Cetol Log and Siding finish is made differently now or not. I've never been a fan of PPG paint products, and I only use them when I'm forced to.
I did work on two log homes last summer, and I used Benjamin Moore Arborcoat semi-transparent stain on both of them. The only exterior stain products that I use and recommend are Ben Moore. These products, both water born and solvent based have performed as advertised in every application I have used them, which is probably every one possible on a residential home, including logs, log siding, cedar siding, trim, treated lumber and cedar decks, fences. water born or oil based? that depends on what you have now, and what your circumstance requires. as a general rule, we can put water based products over top of oil, but it is ill-advised to put oil based products over water born.
If you have always had stain (I'm assuming you mean semi-trans or semi-solid), I would encourage you to stay with that type of product. Long term maintenance will be more predictable and more manageable so long as you continue to use a non film forming coating. Any type of film forming coating, be that solid color stain or house paint, can peel.
Like I said, preparation is the whole game, particularly with something like logs or aluminum siding. Proper cleaning is probably the most important part of any whole house custom repaint. You will need to wash your house, and you should use a pressure washer, although a "soft wash" is what we are usually doing when cleaning a house for painting. PM me if you want more specific information about any of this.
