They are stronger but as with all things Jeep, you should question whether it is "necessary" or just received wisdom and whether your epensive hobby could use that money on something else.
2 piece axle shafts can happily last 30 years behind a 304. The problem comes when for some reason the torque on the Axle Nut starts to slacken and the parts start to move and fret, sudden failure often resulting. This can be brought on by big tyres (37" plus) which put a a lot of leverage on the flange. If you have 2 piece axle shafts which are fine, do you have to replace them for the axle seal? Is it the seal which has worn out or something more dramatic that requires new axle shafts?
If I was having to replace the 2 peice axle shafts, say because one had spun its flange, I would strongly consider single piece axle shafts. I didn't last time due to cost and delivery times.
BagusJeep lives in Bali.
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE