I've tested ridden several bikes and have liked the Shimano components on entry level bikes versus the SRAM system. It seems that you can fine tune and adjust the front derailleur (from the shifter) on the Shimano and not the SRAM as the biggest difference for me.
Another question I have is whether the Shimano 105 components are noticeably better than the Tiagra components. Any comments would be appreciated.

This is a big ole can of worms, but:

1. You can definitely adjust Sram. I dunno exactly what you mean about 'not being able to fine tune the FD,' but you can. Are you talking about cable tension? Perhaps the bike with Sram you tried had cable tension adjusters in an odd place.
2. That's another up for debate question. Basically it boils down to: It's better, but it's up to you to decide if it's enough for you to care. Subaru vs BMW. One is objectively better, they're both good. Some people are 100% honest to god happy with a Subaru, but some people think the BMW is worth the extra cost difference for that little bit extra. Same issue.

SRAM is adjustable all day long in many ways, barrel adj. as stated above and also reach. Like is subjective, both shim. and sram are xcellent high quality systems. In some respects, I would give sram a one up in quality....they use metal internals at lever and their hard anodizing over upgraded metals is surperb.
105 is shimano's entry level race system and yes, it is better than tiagra in shifting performance, weight, durability, etc.

SRAM can be adjusted....I did it yesterday while riding...new cables...I like it better for a number of reasons but ride what you find the most fun.

All the groups work pretty much equally well, and as a practical matter it makes little difference which one you use. It really boils down to taste and how much you are willing to pay to shave a pound or so off the weight,

OP must mean the Trim function of shifter per FD.

Noticeably better? For whom? For an entry-level rider? Probably not.

properly adjusted you probably won't see too much difference.

I definitely have noticed a difference between my Dura-ace cervelo vs my 105 specialized over the past few years...never had any issues with my Dura-ace and shifts just so smooth and quickly but the 105 was always good and not an issue. I don't notice much difference between the Ultegra components I have now on my 2012 Roubaix vs the 105 components I had on my Allez. I do know my Roubaix is (in general) much lighter and tighter and stiffer than my Allez so it feels a lot faster. I assume the weight difference in components helps to contribute to this.

if you can afford it I would step up to 105 just so you don't want to upgrade sooner than you really need to.

This. No SRAM doesn't have the trimming function, but if set up properly, you shouldnt need this even cross chaining.