I've been using the modular gear (Randall, Egnater, and, more recently, Synergy) on and off for going on 10 years now, so I have some insight.
The SYN-50's power section is essentially that of a Fryette PS-2, which can be good or bad depending on your preferences. Personally, I preferred my Egnater MOD 50 to the ultra-clean, stiff, sterile SYN-50, as it has a bit more "bounce" and character.
On the other hand, MOD heads are hard to find these days, and the more common Randall MTS amps aren't in the same league as the Egnater or Synergy in terms of build quality. (They also use comparatively cheap CMEC transformers instead of the Heyboers in the Eggie, which makes a noticeable difference.)
So, to sum up, if you're looking to get into the modular scene and can't find a MOD head, the SYN-50 is probably your best bet. Just be forewarned that Synergy has a bad habit of announcing new preamp modules and then not releasing them for months, if ever.
In any case, good luck.