Some good choices for a 4 stroke.

Saito 56 for normal overall good flight.

Saito 72 for all out crazy

Magnum 61

O.S. 54

YS - not really sure what size they offer now.

Advantages or disadvantages are very much a matter of opinion, less annoying sound , a little less mess, the Saito 56 will do a little more run time on same amount of fuel and perform pretty close in this particular aircraft. Sense the 4* is really not made for speed you should be able to get about the same speed using a higher pitch prop .

Because of the RPM differences there is really no way to compare which is better, its a matter of what the pilot wants. Comparing the two is almost apples and oranges.

IMO it would be worth it to use a 4 stroke simply because of sound and mess, but if the 46sf is working o.k. why fix it.