There are many many options. I'm personally not a fan of vinyl, the corners seam badly and they can crack easily. There are a lot of glass options as well. I suggest that you locate a builder's supply center, this is not a big box store like home depot, but a supplier for builders. They usually carry several brands and can give you unbiased opinion based upon their experiences and can help you with reputable installers. You should come armed with photos of your existing doors, and the house exterior in general. Approximate sizes and exterior exposure, North, south etc. They can help you walk through the different options that are best for YOU. You will have a chance to see the displays of several different manufactures in one space.

Mostly good advice above, although the comments about vinyl don't ring very true. Can't say that I've replaced anything "cracked" under warranty in 20 years, and the welds look much better than they used to. In fact, there are vinyl products on the market now with hidden, butt-joined welds that look pretty fantastic.

Ultimately, each material will have different pros and cons. Wood is rich and beautiful in appearance when stained, high end vinyl will typically offer better performance (thermal and structural ratings), better warranty, less maintenance, and a lower cost. Fiberglass is more of a niche material, but can be a great option if the circumstances fit.

On the "wood/clad" question, it sounds like you are referring to roll formed clad aluminum exteriors vs extruded aluminum exteriors. Most manufacturers have moved to the latter as it is superior. It's stronger, and keeps moisture off of the internal wood surfaces which is why so many wood clad windows and doors rot out in 10 years.

Fiberglass doesn't really bring anything to the table that cannot be had with the "Big 2", vinyl and wood. There are some excellent performing fiberglass products coming out of Canada, but most of the stuff state-side doesn't present anything compelling, again, unless it fits a narrow set of circumstances. The long and short of it is this: Wood is better at being pretty, and vinyl is better at being energy efficient, cost effective, and low maintenance.... These comments refer primarily to a full fiberglass product. If you are looking at fiberglass construction with a wood interior, something like a wood/ultrex Integrity, wood/fg Pella Impervia, and the like, I'd lump them in with wood clad products personally. Still have interior maintenance (primary risk is condensation), and you are choosing form over function. A full fiberglass unit is kind of the worst of both worlds (not as pretty as wood or as efficient as vinyl but still has the high price and generally lesser warranty), but let's say you want a painted interior other than white. If I was shopping for a window or sliding door that could be painted gray, I'd definitely lean toward fiberglass over wood. You lose the beauty of wood when its painted, and fiberglass won't ever rot.

Homesealed what door is that? If thats welded it Looks great.

It is an Okna Forrester series. Butt-joined weld vs. mitre weld (exposed).

^^^ what he said

This is very helpful. Thank you very much.

One of the things I had been thinking about was that I always hear that vinyl is so unhealthy and bad for the environment. I'm not sure that this is the place to ask about that, but if you happen to know the environmental/health issues for vinyl vs. fiberglass, please let me know. Thanks again.

uPVC (i.e. what is used in windows and doors) is quite inert in its finished form. Just as safe as anything (if not safer) out of fiberglass.

+1. This is pretty much a scare tactic and could be used by anyone peddling a specific material compared to another. A vinyl guy could talk about the fiberglass resins, or the preservatives in wood windows, or the painting on other materials, etc... None are really much better or worse than the next as far as environmental concerns