Purchasing a kiln is one of the most important purchase decisions to create with metal clay. The price of a kiln is a major investment, making sure that it meets you current & future needs can lead to stress and confusion.
So putting aside the technical data as you will most probably be looking at the most recommended kilns like the Paragon SC2 or Kingpin 88. in assessing your needs, let's address do I need / want a viewing port &/or a bead door?
To answer this question, you need to identify your current and future possible needs. Of course the capacity to fire fine silver is the most basic requirement, so let's look at the other possibilities. Are you planning on;
Enameling? A viewing port and bead door can be very useful. The more you use enamels, the higher the consideration you should give to this option. Occasional use of enamels, consider the next points.
Glass Work (Glass Fusing, Glass Painting Glass Slumping)? If you plan on creating using glass (not firing glass & metal clay), then you could benefit from a bead door and viewing port. However, most glass-workers find that they don't actually use the kiln to make beads, but use their kiln for annealing their glass. This does not require a bead door, but the viewing port can be useful.
Working with Base (Copper) / Alloy (Sterling Silver, Bronze, etc.)? For a metal clay artist, this is a CRITICAL consideration. Although an insulated bead door will have a minimal impact, it can become a source of heat loss over time and use. This could have an important impact on the successful firing of base / alloy metal clay. So if you don't plan on using it, it's probably best to avoid the additional expense.
China Painting, Lost Wax Casting or Low-Fire Ceramics? are all possible usages. A bead door can be very useful for these crafts, however this will be determined by the potential size of your intended projects. A viewing port in this case is a real plus.
BEAD DOOR: A degraded bead door can also contribute to inaccurate temperature reading resulting in hot spots or cool spots. Kiln "hot spots" can cause bubbling in fine silver clay or even melting!
VIEWING PORTS are made of GLASS ( Paragon indicates "guaranteed up 2300 F / 1260 C"), so this should have a minimal impact on attaining the temperatures required for base / alloy metal clay. But, as with the bead door, it can become a source of heat leakage with the potential of negatively impacting firing.
Keep SAFETY in mind: If you purchase a kiln with a viewing port, you need to protect your eyes from the thermal radiation! So don't forget to purchase #3 Shade Safety Glasses @ the same time as your kiln (you wouldn't want to forget now would you?)
You may be inspired to "eventually" develop other complementing arts skills, but the reality is intention can easily be held for many, many years. You'll be much better positioned to evaluate your intentions when the time comes to invest in a replacement kiln door. Replacing your kiln door requires very little technical skill or tools, so don't let this intimidate you.
When the time comes to make your investment, reflect on the point.
In the end, only you will be making the decision. At least you have this information to help you make an "informed" decision..........So go for it!
Thank you for making this world that little more beautiful with your creativity.