Don unfortunately there is as usual, no easy answer.
The slimline twist is probably the most popular, primarily due to the low cost of the kit.
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sell dozens of different styles with a wide range of prices. While each pen style usually uses it's own unique set of bushings, different plating choice paired with different woods allow you to make a variety of looks with the same bushings.
Some kits like the slimline and other similar kits based on a 7mm drill/tube can offer a more personalized look by being able to shape the profile between the bushings. Other styles don't allow for much more than turning away waste from bushing to bushing, ending with basically just a straight barrel, these styles usually benefit from a more figured wood.
There are higher quality kits to be found but you wil pay a premium for them, Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to
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If you haven't turned pens before, I would start with a slimline and see how you like the process.
IMO There are some pen kits that are far more about the kit than the wood turning, (not my cup of tea) if you continue turning pens you'll eventually find the balance or style that fits you.