No its not just a bling factor.....there are reasons behind a top mount design vs other designs. Each design in most cases has its advantages and dis-advantages. Either it be performance or price point.
Not written by me but a very good explantion of different manifolds.
Credit: Schister66@ HT
Log
-The cheapest of all the manifolds. Log manifolds can easily be made to allow AC and power steering. A log manifold will spool up a turbo rather fast because of its short runner length, but due to it being less than ideal for high volume flow, top end power on a log can be greatly restricted. Logs such as the Inline Pro have a rather good design and ARE able to flow quite well at higher RPMs. A log will work perfectly fine for most street setups...especially stock block
Mini Ram
-Built with a 4-1 collector, mini rams flow better than a log and are still fairly compact and inexpensive. These manifolds are a good mix of short runner design (quick spool) and better flow at higher RPM. This is what i run on the street...i would recommend it for most people who DD their cars, but want better overall flow than a regular log manifold.
Ramhorn
- More equal length than the last two. Ramhorn manifolds have longer runners; therefore, taking longer to spool, but runners are closer to being equal length (better top end flow). Since these manifolds are bottom mounts, it is more difficult to fit a large diameter downpipe or easily manipulate the turbo.
Topmount
-The blingest of all manifolds apparently. A topmount is generally very close to, if not completely equal lenght meaning all runners are the same. This is important because of the cylinder exhaust pulses. Rather than overlapping in a non-eq manifold, in an equal length topmount, all exhaust pulses enter the turbo uniterrupted. This allows the most efficient use of exhaust energy without having deadspots created where there is no exhaust energy in the turbo...even if it is for just a millisecond. Topmounts are generally able to accomodate 4" downpipes and larger turbos due to the placement in the engine bay. For those of us who "need" a Borg Warner S372 under the hood, this is the ONLY choice.
Spool
1. Log
2. Mini Ram
3. Ramhorn
4. Topmount
Overall Power Potential
1. Topmount
2. Ramhorn
3. Mini Ram
4. Log