I would take an LS swap every day of the week and twice on Sunday over an antique 'vintage' 454.
There really is no comparison. Yes, you can make big power with a big block of any displacement, even a 396 or 402. Large chamber, canted valves so they breathe decently stock, but slow, inefficient chamber design, requires more timing lead. Higher emissions, heavier rotating and reciprocating assembly. Heavier valvetrain, reducing potential RPM capability, but will make up with sheer cubic inches and torque down low. Big reduction in fuel economy... figure 10 mpg empty.
Retrofitting a hydraulic roller camshaft can be done, but not inexpensive to do so. Vortec era 454 already has a hydraulic roller cam, but TBI era has a hydraulic flat tappet.
You can still make good power with a hydraulic flat tappet cam, but the trade off is life expectancy when the seat pressures get higher, higher proportion of wear metals in the engine oil, higher friction, etc. ( roller is around 1/3rd the breakaway torque of a flat tappet )
The aftermarket support for all of the engines is extensive, whether small block, big block, or LS.
On a plus side, the LS engines are cross bolted through the lower skirt of the block, and in stock form can reliably support 1000 horsepower, without resorting to a heavier, high nickel 'bowtie' race block for the older small blocks and big blocks, when the power levels are higher than stock.
LS engines have lightweight valves with beehive springs, enhanced rpm capability.